Maybe it's crazy but I trace some of this back to Polian. Small, fast defense geared towards stopping the pass. Sound familiar? Bills, Panthers and Colts all fit this while under his watch. Interestingly, the Colts Tampa 2 D was Dungy's creation, but his Ds in Minnesota and Tampa had a bigger more physical front 4 than he ended up with in Indy.
Also, although I agree that Corey didn't get the most out of the defensive personnel he had, SB XXV was not his fault. The Bills should've won that game- just needed to make the kick. If Vinatieri misses is Belichick's a hack?