https://americanhistory.si.edu/explore/stories/how-santa-brought-coca-cola-cold
Coca-Cola wasn't the first manufacturer to try and use Santa as a lead-in for their product. Ivory Soap is shown at the beginning of the article. So once the idea of commercializing Christmas took off, everyone jumped on. The reason for Coca-Cola to try a connection was simply to keep sales numbers up during the winter, as they were seen as a summer drink.
Must be an American thing then, to commercialize everything. Santa is used to sell just about anything.