I read through the wordy description and still feel more confused about why they did this. I also feel like missed the opportunity to call their language "Rod" in reference to Nim's original name Nimrod.

I assume they didn't like something about the maintainer or the community.

Nim has a plan to add incremental compilation, saving the compiler state in files with the .rod extension. So naming a derived language Rod would be confusing.

It's a bunch of people who like working on the compiler, working on the compiler. Nim proper doesn't have as much flexibility to make breaking changes, and this has limited much-needed internal refactoring.

There was a falling out between some developers on the Discord that led to personal attacks and an eventual banning a while back. If I recall, nimskull started shortly after, and has attracted a few other compiler developers since.

There is no singular "story" here, mostly several former contributors decided for one reason or another (of course there are a lot of small "stories" behind this, but writing them all down would just come out as being "disgruntled people" (as already theorized in one of the top comments) to most readers) to spend their own time in a different projects.