Coca-Cola itself claims to have come up with the "image of a warm, friendly, pleasantly plump and human Santa." Gee, too bad Little Corporal cartoonist "W.O.C." didn't think of that way back in 1869:
Or Julius Bien & Co., when they made this postcard way back in 1908:
And what, pray tell, is warm, friendly, or 4XL about this circa-1909 image?
Or this one, from the same period (postmarked 1908)?
Here's another one, also postmarked 1908, which loudly and clearly makes the case that a fat, friendly, and human-looking Santa originated with Coca-Cola in 1931, Why, this skinny, clean-shaven lout looks like someone who would drop stink bombs down the chimney and film the resulting panic with his Smartphone, laughing all the while:
Thanks goodness Coca-Cola came through with a plumper, kinder Santa in 1931. The world was waiting for one. Oh, by the way, and to its limited credit, Coke doesn't claim to have come up with the red suit, though I don't see why not. If they're going to take credit for the fat, jolly, and human-looking aspects, why not toss in the suit color?
While we're on the subject of Santa postcards, here's a circa-1910s card which appears to combine Santa with the Norse god Thor (and vice versa). Actually, as you may already know, Thor is regarded as one of the many Santa sources. Red suit, white beard, chimney, etc. The guy we know as Santa is actually any number of mythical figures. All of them invented by Coke.