Why did Spagnuolo stink as Saints' DC? (merged)
To build on that obvious truth, there also weren't any truly elite defensive linemen on the team back then, as he had with the Giants. We had Will Smith, who was solid but not elite, plus a bunch of other guys making money but who weren't elite. Excluding Cam Jordan from that statement, as he was just in his second year; was referencing only the more experienced players at the time.
Also, 2012 was the bounty fiasco season and all the distractions that went along with it. Only reason we got to seven wins that year (actually had rebounded to 5-5 and competitive with the Harbaugh-coached 49ers in game 11 until a coupla unforced errors) was due to Drew Brees' greatness.
Payton brought Spags on board a month before the bounty fiasco hit, so there was obviously some sort of plan there. But it didn't have a chance to bloom, unfortunately.