Bill Belichick and his defensive genius is why they had/have a dynasty. BB is the MAIN reason this team has been competative year in an dyear out for the last decade. Any decent QB would have (and has had) great success on this team.
Check BB's record w/ and w/o Brady, Brady rescued BB's HC carer or he'd be a DC somewhere. Also check all the chokes those supposed "great" Ds have had in postseason only to be rescued by Brady including the SB against the Giants 4 years ago.