am a trans guy but am friends with some trans girls + simply like thinking about how communities like the trans community work, and:
firstly, "autogynephilia" isn't a thing, it's an outdated term. it was used in the past to make being trans (specifically for trans women) seem like a mental disorder. using it doesn't help anyone.
secondly, it's just that a lot of trans folk noticed other trans ppl who liked anime, and this leads to a strong sort of connection where you're connected by the fact that you are trans AND by the fact that you like the same sort of media. helps form a community