4chan has had several large demographic shifts that have allowed out-groups to dictate the dominant culture on it, especially with the original founder basically having given up on serious moderation after 2010.

In a way, it's the natural consequence of the internet ecosystem shifting, and 4chan usually drawing its userbase from larger communities. Outcasts from sites like SomethingAwful and YTMND became outcasts from smaller forums, which became outcasts from social media.