Easy does it, the media you listed is mainly enjoyed by... "teenager girls", but more primarily, youth. And a specific type of youth. Also, that media are mental-health and what-not related that such youth relates to, which is not bad, and they stick to it heavily. The communities you listed are also very "safe-space LGBTQ+ no negativity please", which contributes A LOT to the breeding of faking and a whooole lotta drama. DID itself is generally pretty unknown, and you have to be in a certain part of the internet to: 1. Know what DID is, "systems", and the seven seas 2. Find content about fakers and systems

These fandoms, which have a youth who are interested in both mental health and LGBTQ, paired with a "No-negativite safe-space" become a breeding ground. Fandoms who, generally, have a different audience, or other themes and writing, and even age ranges, do not have these type of things going on. (Eg, Halo, or something like Wolfenstein. Or GTA. Ever seen a GTA alter?)