Drepper was an asshole and people eventually routed around him, yes. The system worked. What people forget, too, is that Drepper's problem wasn't just an obnoxious personal style, but a ridiculous level of technical conservativism that led to critical bugs remaining unfixed for years. It was the latter problem that eventually prompted people to fork glibc, not the former.
NetBSD -> OpenBSD
I know very little about NetBSD and am a great fan of OpenBSD.
But Theo is a very horrible person who often attacks people in a personal way for disagreeing with him. I got into a stupid argument with him over fundraising - a subject where I have deep experience - and it was quite bizarre. He had a set of assumptions and disagreeing with them got abuse from him, and some of his minions on the OpenBSD-Misc list, and (I was astonished) abuse in my INBOX from throw away accounts.
What an arsewipe!
And FreeBSD -> DragonflyBSD. Same story.
Actually, the best example of a project where the leadership of the project was so toxic as to drive away potential contributors would probably be glibc under Ulrich Drepper, which got so bad that most distributions abandoned glibc for the eglibc fork. (See https://lwn.net/Articles/488847/ for a high-level discussion).