You have to remember that there are 3 different saints here.
1. Saint Nicholas or Sinterklaas (from where the name Santa Claus derives) was actually the patron saint of seamen, and also of Holland, at the time when it was a great seafaring nation. Every year on Dec 6th in New Amsterdam (later called New York) the Dutch community would have their national celebration and give sweets or dry nuts to the children, a tradition still held today in many parts of Europe. This has nothing to do with Christmas but happened to be close. And of course St.Nicholas was an austere, dark and skinny figure. I believe he was Syrian.
2. St. Basil, who still gives presents to orthodox children on 1/1 was born in what is now Turkey. He was a very wealthy man and was not original a Christian. One day he had a vision, and converted to Christianity, giving all his possessions to the poor. Legend has it that he baked a huge pie and put in golden rings or precious stones. And then the poor people choked on it (j/k). Greeks still make such a pie on 1/1 and call it “Vasilopita”. They put a coin in it, and whoever finds it is supposed to have good luck for the rest of the year.
3. The spirit of Christmas (not a human figure) and Father Winter (a rather malicious old man) got combined into Father Christmas, an imaginary figure who is actually the closest to the modern-day Santa. He brought children presents on Christmas Eve and came in through the chimney, in the form of the wind.
4. And of course Coca-Cola took all of the above and made loads of cash :)
(as you probably know, it was they that first dressed him up in red and white sometime in the 1920s).