Funny story, I was once on the periphery of a bit of fandom drama (I won't say which TV fandom cause I don't want to trigger/dox any crazies) where a particular fandom artist/fanfic writer wrote a popular fanfic with accompanying art. This was successful enough that some other artists within the fandom drew their own sincere art of that fanfic, with appropriate links to the original work.

The author flew off the handle, blocked them all, sent takedown notices, and posted an epic rant about how they were using their intellectual property without permission. When someone (cough) pointed out the hypocrisy of them trying to assert ownership of a setting featuring characters that they themselves didn't own or have permission for to begin with, they claimed that it was different because everyone already knows the TV show and it belongs to the public, whereas their fanfic of it that they published online was personal to them.

I don't know if there's any moral to the story beyond artists are weird and sometimes psycho

This is how it came across to me too but maybe there’s context I’m missing.

A younger or less-experienced person comes up, says “I drew this like you draw!” and you’re mad? That’s a you problem.