Justman was really frustrated and angry that GR turned his back on the series, and I don't blame him one iota.
Justman cornered GR one day and bluntly told him that the good ship Enterprise was in deep trouble. GR very briefly assumed command again, but then just as quickly faded into obscurity as far as production was concerned.
Sources, please.
BTW, you can fire a show's creator from their show in the right circumstances, but they still own it and they still have to be paid and credited. Them's the legal realities. Also, as I've said several times, it is commonplace for show creators to move on after a couple of seasons. They need to work on getting other shows on their air because if the current show gets cancelled, they're left holding their hats.