This is a really, really good point. The crappy Saints coaching was really bailed out by Brady being a terrible QB. Or maybe another way to look at it is that Peyton realizes that Brady is washed, and essentially was just willing to put the game in the hands of his defense, knowing 1) the Bucs would make the boneheaded mistake of trying to rely on Brady to save the day, and 2) that his defense would make them pay.
So really, both Sean Peyton and Brady suck, one way or another. It was just a matter of whose screw-up would overwhelm the other's.