While I don't think ReNPC's anti-ism is necessarily connected to Mori using a different artist, I do feel it's worth preserving the context of
why people are bringing him up in the first place.
So back in Hololive EN's early days, a certain fanartist started getting attention from the girls due to his talent and dedication. I think what drew Ame in was his whole "holoen MLP models" thing. Either way, Ren began to be contracted as a background artist for Ame and word about him spread through the company, leading to him being hired for some of Gura's backgrounds as well. This was pretty consistent from around the time of EN's debut to mid-2022.
Then something changed. He was starting to try and draw attention from some smaller creators - first it was Pippa, then Shondo. Shondo in particular quickly grabbed him by the balls and he went full Shondophile. Most of his art around late 2022 was just her specifically. If memory serves she was what kicked off him drawing straight-up loli porn.
Either way, while he was mostly a fan of Shondo, he still drew fanart of the HoloEN girls from time to time, usually Fauna or Ame. Then seemingly out of nowhere, on an alt account (since his main was banned at the time), he drew this.
[a]
Per his own explanation, the art started as "a funny idea to start but now it just makes me feel sad for the little shrimp". But a number of chumbuds saw it as him straight-up mocking them, especially considering he did so directly on her art tag.
Fast forward to Gura's birthday, he tweets this in response to her tweet about it.
[a]
Now, regardless of how you personally feel about mocking chumbuds and/or Gura, saying something like this on your main account towards a talent who formerly hired you just sounds bitter and disappointed, like he couldn't find an "in" with the talents (unlike, say DuDuL). So most people have speculated that he has been officially blacklisted, either for this tweet or (more likely) for the pic before.
Interestingly, he also seemed to have stopped drawing Pippa by mid-2022. Last thing he ever drew for her was a thing in december for a compliation video. My personal assumption is that his own obsession with Shondo has just overshadowed any potential work he could've gotten from his former clients. I've heard a few rrats about the fact that he's trying to genuinely groom Shondo too.
So it's been interesting to see his own slow degradation from being passionate about the Holos to full on indie-grooming. It's worth keeping an eye on him, since he draws a number of other 2view loli vtubers.