We also need to take in accound, Allegri isnt a big boss flamboyant coach. He inherited a winning team from a coach widely considered far superior. Good luck changing your defence completely and have the players believe in it.
Instead, as the season goes on, it keeps improving steadely.
I think Allegri loves beeing here. Able to keep a low profile, quality players and a general manager that isnt selling your stars and fucking your daughter without giving anything back