Allegri was the type of manager they should have kept. I do not think that they fired him for "not being successful" because he did improve the team compared to last season. I think he was fired for not listening to the club heads, the owners and so forth, they disliked him and fired him as soon as they got the chance.
They probably wanted to fire him even earlier, but he did alright with the team all the way until the end. If they won their games on the last month, they would have been as high as second place, so he was doing good. Only reason they fired him so late was because he did great up until the last month. Him staying at this club for a few more years, could have made this team better long term.
THIS! I have said this before, and I will be adamant to support Allegri. Yes they had a trouble by the end, but he took that team from 8th place to second place for most of the season, just because he had ab ad ending to he season, they shouldn't have fired him. He could have brought them even higher and higher given enough time.
The fact that they did not have enough time to give him, and they just fired him makes no sense to me. Who are they going to get that would be a better manager than Allegri?