Their infringement is different, and would really be a trademark issue if we hadn’t just invented the idea of copyrighting a character separately from the story they are a part of in the ‘30s (they are not individually copyrightable under the original text).

There’s a substantive difference between ingesting other people’s work and hosting copies of fans knockoff models of their favorite characters.

It’s even weirder because in other mediums this wouldn’t even be a thing. Nobody gets nearly as up in arms about fans doing their own cuts of movies, or re-using characters in written fan fiction, or etc. Very odd to me how up in arms people get about this specifically for visual art.