It is indeed very strange.
My guess is that it started out as something to make fun of Vtubers, but like many plagued threads eventually was subverted into becoming a fan thread about the topic itself.
As to why it's a thing, the fact is these people are a little...limited. They wouldn't be engaging in the hobby they are otherwise. As such the likelihood that any of them are going to be able to run a discussion forum of their own is pretty low, and if they tried it would absolutely, immediately, within probably a week, be taken over by trannies who'd subvert it to be about their pet political/social issues.
As such they have to come here to KF to be granted the freedom to post without the constant fear of some castrated subhuman idiot coming in to dissect their verbage and ban anyone who looks at them sideways.
So personally I see it as charity. Captain J Moon dislikes the animes, but he dislikes seeing people stifled even more, so the retards are granted their own little retard pen where they can go on about their retard shit free from molestation by tranny jannies, with the only trade off being yelled at or made fun of sometimes.