alt Hacker NewsI think part of it is due to corrupt government regulating internet as if only Facebooks and Reddits were on the market. It destroyed niche forums and made the place less democratised. Today you cannot just rent a server and start a forum without massive financial backing and therapist on speed dial.
Did you know that if you just run a forum you don't go to jail for that? First the police have to notice you in a negative light for any reason, and second they have to bother to do something about it, and thirdly their first interaction with you is more likely to be "oi! stop doing that!" than anything else. What killed them isn't the law, it was firstly centralisation pressure, and secondly our own paranoia about the law.
And if the government wants to arbitrarily get you, it can do that with or without you running a forum.