1) We didn't have nearly as much talent as we have recently.
2) He didn't scheme around the talent that WAS there (ie Patrick Robinson was awesome in 2011 playing bump and run man coverage. He was historically bad in Spags zone scheme in 2012)
3) We didn't have a head coach.
He was also forced to keep Sean's boy on his staff and not bring any of his own people in. Not only was his scheme too complex for the players, it was also too complex for the likes of Johnson, Vitt, and the like.