Ever wonder why Lovie Smith coaches a 4-3 defense? In this excellent USA Football video (h/t Field Gulls)m he explains why. The video hasn't exactly been seen much (the YouTube version has all of 90 views), but Smith perfectly states his reasons for loving his defensive system: it allows his players to specialize in certain roles.
Some teams want generalists. They want versatile players who can fill a lot of roles. Greg Schiano did some of that: he tried to turn Adrian Clayborn into a stand-up linebacker who could rush, run and cover, his cornerbacks had to be able to work the slot, his safeties were largely interchangeable, and everyone had to be able to blitz and cover.
Other teams want specialists. They want their defensive linemen to rush the passer, and their linebackers to drop into coverage. They want their cornerbacks on the outside, and their safeties deep. They want to be able to drill specific tasks over and over again until players can execute them to perfection -- and that's where they get their edge on the football field.
That last school of thought is where Lovie Smith comes from, where Tony Dungy came from -- and even where Bill Belichick comes from, as he consistently uses players in limited roles and specific subpackages. This school of thought tries to win by out-executing you, while the first school of thought tries to win by tricking you. Lovie Smith does this, too, as he states himself, as can be seen in his training slot cornerbacks as a separate group, and his emphasis on pass-rush specialists on the defensive line.
Either philosophy works, and neither school is as pure in doctrine as I present them now, but one of the core thoughts behind the Tampa 2 is to get specialists, give them simple rules, and hope that allows them to play fast on the field. That simplicity doesn't leave much room to bust coverages. It doesn't rely on complicated blitzing schemes. It doesn't require players to spend two offseasons learning your scheme before they can properly execute it. You just get good athletes, plug them into your system and watch it blossom.
If that sounds simplistic, that's because it is. The Tampa 2 isn't complicated, either as a coverage or as a general philosophy. Football is only as complicated as you make it, and the Bucs prefer to keep it simple on defense. But that philosophy has led to stellar defensive play nearly every year Lovie Smith has coached in the NFL.