Slenderman stories never really stopped because the character had already become detached from any single creator or incident by the time 2012 happened. The creepypasta community is basically built on remixing - people take the concept, twist it, add their own lore, and pass it along, so there's no central "official" version that could be killed off. You still see Slenderman stuff floating around, especially in horror communities and indie games, though maybe not with the same mainstream meme energy as a decade ago. The stabbing case was tragic and definitely made some people uncomfortable sharing it openly, but it didn't erase the character because he was never really owned by one story in the first place.