1. Stop conflating Twitter with reality. A majority of their viewers are not rabid Twitter consumers. MOST PEOPLE ARE NOT CONSTANTLY ON TWITTER. TWITTER IS NOT REFLECTIVE OF REAL LIFE.
2. The company gave him permission, the girls barely knew about it. This is the Cruz of the miscommunication that caused the whole problem.
3. Personal opinion time: I get the feeling most Vtubers don't really like Nux. They tolerate him because he's popular, but his style of content (i.e. mining them for drama and content) probably rubs a lot of them the wrong way. Also, that he likes to pretend to be some kind of Vtuber vigilante, protector of the community, by inserting himself into situations he's not actually part of and using it to paint himself a hero, probably doesn't sit well with a lot of them either. The situation with Melody and the legal issues she was having with her models original artist is a perfect example. I imagine her legal team was freaking with the situation for a while, and she was obviously embroiled in this shit, then once it's all said and done, Nux comes along and puts out a video like, hey guys Nux here, see all these problems Melody was having, well now that me and my Cuh-razy fanbase are her to protect this poor damsel in distress, she shouldn't need to worry about all this anymore! Because of me! Damn, isn't it so great for Melody that I exist!
Like imagine that shits been going on for years, plus whatever is going on behind the scenes, and yeah, the girls just got sick of it and blew up. This was a culmination of having to deal with his dumbfuckery, not just one issue, and they blew up.