Great points raised, especially from blueleopard about team cancers.
The Pats, Colts, and Steelers are the 3 teams that come to mind that had as realistic a chance as anyone at repeating the last 5-10 years. In the case of Pitt and NE, they've had very hard nosed no nonsence coaches that don't let their team skip a beat.
With NE and Ind, they have extremely driven QBs, and with Pitt they have Troy P who also do not let their teammates slip.
So IMO 2 big ingredients in the are leadership through the coach and arguably just as importantly, 1 player on the field. Consequently, I think the answer to RP's question lies in Rodgers' hands.