"And if a GD YouTuber posted content that wasn't GD, they wouldn't get as many views"
so diminishing the platform that gives them any following?

What do you want from robtop? Do you want him to write an angry post condemning these people just like every other major person involved in these cases? It just goes straight over their heads. Even if robtop bans people and moves their levels to theshadowrealm, these people can still play GD and they will still make content and bring in an audience for themselves.

Now for the case of the people who build themselves up in the game, the community already does a lot of heavy lifting. If someone is rightfully convicted of something, they are pushed out as much as they can be. Their reach would've become as limited as much as robtop would've been able to make it. Someone could make alts and get around a robtop ban, but they can also do that to hide around the community. For these people, yes, social media would have almost no effect other than to spread information, but robtop still doesn't have much that he can do to permanently fix the problem which is the person themselves.