The majority of this team was drafted by him and his savvy FA signings like Jensen, JPP, Suh, and Shaq, not to mention getting Brady and Gronk in here. Give the man his props, it took a while but he has constructed a really good roster.
I personally think the turning point was the hiring of Bruce Arians, because he has been developing the young players very quickly and effectively, not by himself, mind you, but by bringing on all the right assistant coaches. I remember reading that he has like one of the largest coaching staff and that he has like a separate practice for the younger players, or something to that effect. I think this has done wonders, because admit it or not, Tom Brady alone could not have won this Super Bowl by himself. If we were to just point to one thing, it was the defense that won this game, which is in no way, taking anything away from Brady’s effect on the entire team. Brady had them believing that they truly could be Super Bowl Champions. Mission accomplished.
Good point @chad1336. But there was already plenty of young talent for BA to mold when he and his staff arrived. The coaches obviously have done a good job developing the young players, as well as unifying this team into a championship team.