I can relate a story about a similar situation. Some years ago a front office type made a acquisition without notifying or getting the approval of a NBA coach. The coach was furious because he wasn't consulted and responded by never playing the new player. "No offense, Man, this is between me and the FO."
I suspect something similar happened with the new FO guy who took over for RC not understaning the realities of life. He had the power to sign, but not to make the coach play Carroll. You can bet that the new guy will do ANYTHING to get rid of Carroll to keep from losing more face for the next two years. That of course assumes he keeps the job past June.
I don't have any inside info, but there can only be one reason and this seems to work.