I have also noticed that a lot of them are fictionkin; this attitude is prevalent in nearly all of the otherkin communities that are not therian or old-otherkin based. I don't know if this has to do with the subject matter of each community though, as therians and otherkin generally don't have "doubles" to fear or kintypes that are hugely problematic, or that people might know about in public media, and otherkin and therian kintypes have a certain level of real-world presence that can't be altered by someone saying "that's wrong". You can't sanitize nature and mythology, but fiction can be deemed problematic, and its participants and creators condemned.

I think the otherkin community was easier to target and take a hold of because otherkin are not taken as seriously and due to that it's easier to distort the community's ideals that way. In a way, I'd suspect it's also easier for them to distance themselves from any personal issues if they externalize their issues into a kintype and prevent people from doing things involving it.

I suspect a lot of them are also following a pack mentality, where they just got into the community and have the chance to "be themselves" and they make friends with people with questionable ideas or who want to use them, and they're radicalized one way or another due to this. They don't know what's normal but they trust that others around them do (or at least can push them in the right direction), and it just escalates from there.