Let's list the decisions of the rebuild that contributed to his getting canned:
1. Patricia/Judge. Trusting that his yes men could develop a first round pick into something beyond a basket case was a mistake.
2. Brady. Bill believed Brady was done, told RKK as such, and then Brady went off and did what he did.
3. ****ty drafts. I think he changed in 2013, post AH, but you can look at his lack of success in the draft as the #1 reason the team couldn't reload quickly.
Those are enough, combined with a 29-38 and an inability to evolve, be it from age, ego, stubbornness or ay combination therein. 70 year old coaches don't get a long leash. Bill didn't surround himself with a network of great coaches to assist him, he kept a small group of confidants designed to carry the message instead of challenge him to be a better coach.
I truthfully believe it was time.