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.