Clearly there was no other decision to make. He was in over his head. He might have eventually learned, but would Robert, the players, and the fans be prepared to continue to have these types of seasons as they slowly rebuild the team, try to attract good players, all the while giving Jerod the education he clearly needs? They've pretty much destroyed most of the equity they gained around the league and the country about the "Patriot Way" - which almost looks like the "Brady Way" now, really. You don't want to destroy all of it with more seasons like what we had, where we got worse over the season, not better.
It's not fair because obviously even when he was unhappy Brady still had a better team than this rolling circus that Mayo had to deal with, but this isn't the right franchise and the right time for him to learn how to be a competent coach. Better off cutting losses and finding the right coach, someone who can at least maximize limited talent than someone trying to figure it out as he goes.
Clearly Robert and the Patriots value continuity. Nobody wants to be in a perpetual hire-fire cycle, that's a recipe for mediocrity, not to mention you need to question your hiring processes if you seem to always get it wrong. But you also need to balance that desire for continuity, for giving people chances, with being able to recognize if you made a mistake or not. I think the proof is in the pudding in terms of that.
But if they are using Jerod as the lone scapegoat whose head had to roll, then that would also be a mistake. They need to get rid of everyone who contributed to this rolling circus, including people like Eliot Wolf, who was one of those responsible for putting this team together. They need to do a review top to bottom and clean all the trash out.
