Coke may have (re)popularised them, but they didn't originate them, so the Siberian shroom santa is still technically possible if not plausible.

Although it may seem a fortunate coincidence, the use of red and white colours for Santa's outfit was not a homage to Coca-Cola's brand colours, but rather was inspired by the Bishop's mitre clothing which may have been worn by the real St Nicholas

https://www.citma.org.uk/resources/the-story-of-santa-and-coca-cola-blog.html