I began noticing a somewhat vague paradigm of evil clowns maybe nearly a couple decades ago. With Stephen Kings' It and random online comments about not being able to go to sleep for fear of being devoured by evil clowns, and then there was that serial killer clown - JWG.
And of course, maybe around a decade ago there were all those random and bizarre encounters with clowns in parts of the US in which I even saw a few YouTube vids. Satanist clowns? Maybe, or just, clowns.