I don’t think it has anything to do with their creative accomplishments. I think it needed clarifying that no one he is not personally involved with outside of work wanted to continue working for him. Frankly you claiming to be confused by that is concerning to me.
There were six writers, and dozens of other people, for most of the development of Disco Elysium. Why would it be any better for just three of them to get the rights? This was always going to be a mess where people got screwed in ways they didn’t deserve. I can say that Kurvitz ended up being the one that got most screwed and that genuinely sucks, but also there was no way it was going to turn out any better. Those things aren’t mutually exclusive.
As for Kurvitz in the future, I don’t know how this will turn out, and it’s true that he can’t write any direct sequels involving any of the characters or locations explicitly in the game, but basically nothing else about the game is even really copywritable. He can still write stories in the same world with the serial numbers filed off. I don’t know if he will. He might spend the rest of his life being bitter about what was stolen from him, but if he wants to go back to what he’s good at he always has that option.