Always thought Bethesda/Zenimax were a bit suspect at best for the way they launch seriously bug-infested games on the public and then prematurely abandon the titles still riddled with game-breaking bugs after them having sold millions of copies.
This latest development just reaffirms that belief in me, lowering my opinion of the company from "suspect" to "bag of cocks".
I have no insider knowledge about this, but you have to be careful on statements from both sides, especially when lawsuits are involved.
The whole affair is, of course, rather unfortunate. John Carmack is certainly rich enough to leave id software at any time. I don't know the reason why he didn't leave Id software when he started working with Oculus VR, but I guess that it's hard to leave a company you founded (especially when all other founders already left).
After the tragic death of then lead engineer of Oculus VR Andrew Reisse, combined with the fact that Zenimax couldn't make a deal with Oculus VR, likely played a major role in John Carmack's decision to leave id software for good.