So, this isn't really proof or a source, but it's possibly more like grooming people who are closeted trans/non binary (or maybe even before they realize they're closeted). So it could be people that already want to be feminine but aren't really aware of it. So imagine a young amab person who's been bullied into being masculine despite wanting to be feminine. Ending up in such a community would make them a target for this type of grooming.

Just thinking out loud how it might go down. Because I agree, I don't think it'd be easy to just convince someone who wants to be masculine to be feminine.