>>127606947 (OP)
In my estimation, there were multiple things. Not just with this guy, but with incelcore in general.
1. The genre became incoherent in its themes. You have "incel" in the name, and then the biggest artists are posting fucking break up songs. How is that incel? Incel is about being a life-long reject without any exes. At that point it just becomes a vacuous outsider aesthetic for "normies" to latch onto, when they want to feel like they're unique, while not diverting at all from the lyrical themes of 50% of pop music.
2. No good albums. There were good songs here and there, but I haven't heard a single good album in that whole genre. You'd think they'd be able to produce just one. A good album is what gives you staying power for decades. Nobody will celebrate you as some fantastic ground-breaking musician in 20 years because you had a single that went viral.
3. There was no novel sonic identity to the genre. It was all just a mishmash of songs in different already-established styles, that were unified by what amounts to a vibe. That's not to say that you can't make good music that way, but in the absence of anything else that's of note, there's just not much to chew on, if you're familiar with similar-sounding music.