Linking an article whose only cited source is Wikipedia does not make something comprehensive or factual. That said, I was wrong about who coined the red suit, but you are also incorrect that Santa was often portrayed in red prior to this.

Reading further into the actual Wiki article, Nast pioneered the red color of his suit into mainstream, however looking at other sources cited, Santa's suit being red is actually attributed to the poem A Visit from St Nicolas (also known as Twas the Night Before Christmas) from 1823. Nast took that depiction as inspiration and put it out on the market and Sundblom did the same for Coca-Cola which cemented it in pop culture.

Based on sifting through multiple other (non-wikipedia) sources and transcripts online, the figure of Santa is based on St Nicolas (from European folklore) who was mostly depicted in white saintly robes with accents of red, Father Christmas (from ancient English traditions) and his clothing was usually tan, blue or green, and Sinterklaas (from the Dutch) who was also portrayed mainly in white saints robes with a red cape/hat. Up until the 1800s, he was very rarely portrayed in red, and that's because up until the Victorian era the myth and depiction of "Santa" as we know today was in the process of growing and changing/melding with other cultural portrayals to get what we have today.

It's not false and I never said he wasn't drawn in red. Prior to the Coca-Cola marketing, he was drawn as a slimmer man in green, blue or red (but mostly green or blue) suits and not always with a giant beard or sack. The designer from Coca-Cola marketed his new design so well that now, we almost exclusively see him as a fat, jolly, bearded man in red. Coca-cola is the reason that when someone says "Santa" the image that most people immediately think of is this and not this or this.

It comes from the Celtic people who used to decorate with red and green holly - holly was supposed to keep things beautiful during the winter and signify the coming spring/new life. The first recorded representation of using the color scheme was in a 14th century church where the partitions were painted red and green around Christmas time.

But then, the guy who Coca-Cola hired to drew Santa took the red and ran with it. He's actually the reason Santa is depicted the way he is (jolly, big man with red suit and white hair/beard). Before that, he was not as big and his attire varied in color.

Edit to add: some people are really mad that I was incorrect about Coca Cola pioneering the red color lol I went on a deep dive about Santa because I have nothing better to do today and the red color of the suit was cemented in this order:

-sometimes being portrayed in red or red accents in historic images -> Twas the Night Before Christmas poem in 1823 -> Nast took that depiction and solidified it after a few different iterations (including a miniature Santa) -> Coca Cola hired Sondblum and marketed the ever living shit out of this image and it stuck with pop culture.

Santa is an amalgamation of three different European mythological figures/saints and stemmed from winter feast traditions and originally was robed in white (with red accents), blue, green or tan, with red becoming more popular in 17-1800s.

If you want more facts and nuance, I suggest looking further than Wikipedia and doing a deep dive yourself. His ancient self from pre-Chrsitian eras is actually a neat and interesting figure.