So, very early, I had mixed feelings about Santa Claus. During a period of instability as a young adult, I experienced the idea (with strong negative emotion) that Santa was invented by (and was an extension of) Satan; their names are an anagram after all, with the exact same letters in a different order. The worldly marketing of Santa for materialistic gain, as well as the tendency of people to focus on Santa instead of on the true reason for the season, provided for me strong evidence that this satanic connection was so.

But then I came to realize the joy that children experience (and that I experienced before the Great Betrayal) and I read the famous newspaper editorial letter, "Yes, Virginia, there is a Santa Claus" published originally in 1897 in the New York Sun, by editor Francis P. Church. Then I did some research on the ancient saints, including the bishops named Nicholas (there were a number of them) and examined the evidence regarding the likely historical origin of the St. Nicholas stories.

So while I still dislike the manipulative materialistic marketing of Santa Claus, I have come full circle and believe that his mythical usefulness is valid even for Christians. Let me share with you some articles and information, including the classic letter to Virginia O'Hanlon. Here is some information I collected many decades ago.

How did the legend of Santa Claus begin?
The popular American name Santa Claus originated as a mispronunciation of Dutch Sinterklaas, which is a contracted form of Sint Nicolaas (Saint Nicholas).
"Father Christmas" is a well-loved figure in many countries and predates the Santa Claus character. Father Christmas is similar in many ways to Santa, but also different. Santa Claus is inexorably tied to Christmas in American culture (via Clement Moore's fun poem), but in some cultures, he is not associated with Christmas Day at all, arriving on a different day (for instance December 6th, the 'twelfth day of Christmas,' also called Epiphany and St. Nicholas' day) while in these earlier cultures, it is baby Jesus who brings presents on Christmas eve.
Probably the most ancient reference is to Saint Nicholas of Myra, a 4th century Christian bishop of Myra in Lycia, a province of Byzantine Anatolia, now in Turkey. He was born at Patara, province of Lycia, Asia Minor. He was very religious from an early age and devoted his life entirely to Christianity. In Europe (more precisely the Netherlands, Belgium, Austria and Germany) he is still portrayed as a bearded bishop in canonical robes. The relics of St. Nicholas were transported to Bari in southern Italy by some enterprising Italian merchants; a basilica was constructed in 1087 to house them and the area became a pilgrimage site for the devout. Saint Nicholas became revered by many as the patron saint of seamen, merchants, archers, children, pawnbrokers, prisoners, Russia, and the city of Amsterdam. In Greece, Saint Nicholas is sometimes substituted for Saint Basil (Agios Vasilis in Greek), a 4th century AD bishop from Caesarea. Also, a few villages in Flanders, Belgium, celebrate a near identical figure, Sint-Maarten (Saint Martin of Tours).

Every December, Christian clergy and scholars from around the world make a pilgrimage to the southern Turkish village of Myra to commemorate the death of that St. Nicholas. This palm-tree-lined Mediterranean port town, in a country that is 98% Muslim, seems an unlikely place for such an affair. But the death of this beloved bishop over 1600 years ago was close enough to Christmas that he became linked to the holiday. Stories of Nicholas's miracles and acts of kindness, most written after his death, have made him one of the most popular Christian saints. Among Greek, Russian and other Orthodox Christians, he remains one of the most revered saints, and many Eastern Orthodox churches are dedicated to him.

Through various legendary stories, Nicholas became the patron saint of children. The most famous account is the one that gave birth to the modern-day Santa. It tells of three sisters of Myra (now Demre) who were too poor to afford a dowry. Their family was ready to sell them to the highest bidders as prostitutes. St. Nicholas wanted to save the girls from that horrid fate but it was considered bad luck in those days to take money from a cleric. So he waited until night, climbed onto the family's roof and dropped bags of silver down the chimney. The silver fell into stockings the girls had hung to dry. Thus was born the tradition of pinning stockings by the fireplace for Christmas presents. In another version, Nicholas didn't go on to the roof, and instead left money outside the house under a tree, and thus came the ancient prototype of the Christmas tree.

The one remaining icon still intact in Demre, Turkey is a statue of St. Nicholas surrounded by children. He has a thick bushy beard and is also rather thick around the middle. In Germany and Holland Saint Nicholas is sometimes said to ride through the sky on a horse, is depicted wearing a bishop's robes, and is said to be accompanied at times by Black Peter, an elf whose job is to whip naughty children. Early Americans adopted the idea of gift-giving from Dutch settlers and eventually merged the Feast of St. Nicholas with Christmas.

How did Santa get so fat?

When the legend of Santa Claus first arrived in the United States, people envisioned him as a thin and gangly Father Christmas in robes. It wasn't until Clement Moore's 1823 poem "A Visit from Saint Nicholas" that Santa came to be seen as fat, like "a bowl full of jelly." (How rude!) Moore's image of Santa was "fleshed out" by a political cartoonist named Thomas Nast, the same man who invented the donkey and the elephant as symbols for the Democratic and Republican parties. It was Nast who created the image of Santa we know today -- the fat, jolly fellow with the white beard, red and white suit, and silly cap. It is true, however, that Madison Avenue advertising executives played a role in shaping our image of Santa. In 1931, advertisements for Coca-Cola depicted Santa as a human-sized figure instead of an elf, and in 1939 an advertising writer for Montgomery Ward created Santa's red-nosed sidekick Rudolph.

Yes, Virginia, there is a Santa Claus
(Editorial page, New York Sun, 1897, by Editor Francis P. Church)

We take pleasure in answering thus prominently the communication below, expressing at the same time our great gratification that its faithful author is numbered among the friends of The Sun:

Question: I am 8 years old. Some of my little friends say there is no Santa Claus. Papa says, "If you see it in The Sun, it's so." Please tell me the truth, is there a Santa Claus?
-- Virginia O'Hanlon

Answer: Virginia, your little friends are wrong. They have been affected by the skepticism of a skeptical age. They do not believe except what they see. They think that nothing can be which is not comprehensible by their little minds. All minds, Virginia, whether they be men's or children's, are little. In this great universe of ours, man is a mere insect, an ant, in his intellect as compared with the boundless world about him, as measured by the intelligence capable of grasping the whole of truth and knowledge.
Yes, Virginia, there is a Santa Claus. He exists as certainly as love and generosity and devotion exist, and you know that they abound and give to your life its highest beauty and joy. Alas! how dreary would be the world if there were no Santa Claus! It would be as dreary as if there were no Virginias. There would be no childlike faith then, no poetry, no romance to make tolerable this existence. We should have no enjoyment, except in sense and sight. The external light with which childhood fills the world would be extinguished.
Not believe in Santa Claus! You might as well not believe in fairies. You might get your papa to hire men to watch in all the chimneys on Christmas eve to catch Santa Claus, but even if you did not see Santa Claus coming down, what would that prove? Nobody sees Santa Claus, but that is no sign that there is no Santa Claus. The most real things in the world are those that neither children nor men can see. Did you ever see fairies [or angels] dancing on the lawn? Of course not, but that's no proof that they are not there. Nobody can conceive or imagine all the wonders there are unseen and unseeable in the world.
You tear apart the baby's rattle and see what makes the noise inside, but there is a veil covering the unseen world which not the strongest man, nor even the united strength of all the strongest men that ever lived could tear apart. Only faith, poetry, love, romance, can push aside that curtain and view and picture the supernal beauty and glory beyond. Is it all real? Ah, Virginia, in all this world there is nothing else real and abiding.
No Santa Claus? Thank God he lives and lives forever. A thousand years from now, Virginia, nay 10 times 10,000 years from now, he will continue to make glad the heart of childhood. [How real is that gladness?]

On Christmas Eve (the other night),
I saw the most amazing sight,
for there beneath the Christmas tree
was Santa kneeling on his knee.
His countenance was different than
that all-familiar jolly grin;
his head was bowed, with hand to breast,
and slightly tucked into his vest.
For there in the nativity
was Jesus and his family,
and as I heard him start to pray
I listened close to what he'd say.

"Lord, I know that You're the reason
I take pleasure in this season.
I don't want to take Your place
but just reflect Your love and grace.

I hope You will let them understand
I'm just an ordinary man,
who found a way to do Your will
by finding kids with needs to fill.
But all those centuries ago,
there was no way for me know
that they would make so much of me
and all the gifts beneath the tree.
They think I have some hidden power
granted at the midnight hour;
but it is my great love for You
which is inspiring the things I do.
And so when they begin to open
gifts for which they have been hoping,
may they give You all the glory,
for You're One True Christmas story.

By Alda Monteschio

And a current article by Sean Fitzpatrick entitled "Ten Reasons to Believe in Santa Claus" is worthy of perusal. https://www.crisismagazine.com/2020/ten-reasons-to-believe-in-santa-claus

HAVE A VERY MERRY CHRISTMAS!