It probably was an old Vaudeville gag the actors knew, like slipping on a banana peel. I imagine it was a success on film over the stage version because people in the cheap seats couldn’t see it well in a theater while a movie’s close-up view made all spots more equal.
Fatty Arbuckle as the first “victim” seems appropriate. He was Hollywood’s first fat guy star and they still tend to be the pranksters or butts of jokes: Chris Farley, John Belushi, John Candy, Oliver Hardy and Dom DeLuise.
Pie-in-the-face moments aren’t very common anymore except in children’s shows. I remember it was a frequent punch line on the Bozo show but Johnny Carson and his players could use it to great effect. Timing is everything. Now that I think of it, activists still attack their foes with them such as this infamous “attack” on Bill Gates a decade ago, I remember commenting on it through Picayune‘s printed predecessor.