If I were to guess, probably the rise in social media has to deal with some of the change, because there is a much wider audience now. In the past if you were a kid who did something "edgy", the rest of the kids would just think you're a moron. Nowadays you can film your escapades and put it on the internet in the name of content creation, and other moron kids can like it and cheer you on.

Vast majority of kids/teens are fine. Social media enables the 5% of morons to get fame, and encourage other moron kids/make certain things look socially acceptable.