Yeah, clowns are definitely a great example of that. They're WAY more associated with horror and negative perceptions than they are with positive ones. Not sure if it specifically started with Pennywise but it's definitely way more of a trend now. But yeah, it follows the formula of taking something that was meant to be entertaining and even funny and make it horrifying and murderous. It can be more effective at being terrifying than something that's brutally upfront about being evil and dark as with clowns and animatronics, that feeling of deception and betrayal is now there, especially with the kind of innocent and unknowing childlike trust that things like that have placed in them.

It also works with locations that were meant to be happy, fun, and relaxing. I've seen plenty of carnival settings go to hell, along with vacation islands and camp grounds. It's easier to make a situation more terrifying if the cast has their guards down because they thought they were in for a good time, not a terrifying one, and as a result, they're totally not prepared and they're desperate.