Not far out of the realm in my opinion. Bill is a genius. Should Brady sustain an injury going forward and at his age they are up a creek at QB. Jimmy G is clearly able and ready and Bill had a succession plan in place that never involved Brady playing into his 40's. He never subscribed to it. The banning of Brady's business partner and trainer Alex Guerrero from being on the sideline and road trips was Bill's signal.
Kraft will rue this decision in the future and they will deserve every bit of the struggle that comes with it.
Belichick won't oversee that rebuild either because his plan was sabotaged by Kraft. Had Jimmy G still been there there would not have been a rebuild from the QB position which was probably the main philosophy behind wanting to keep him. Swift transition with less growing pains.
Now there will be.