Just like the offense with the Killer B's. Relied on the pure talent of the stars. What made the Steelers of the 2000s so good and Super Bowl winners was the perfect blend of star players and role players who worked together, played for each other, and played with an attitude.
Polamalu, Harrison, Woodley, Porter, Taylor, etc. were all able to star because the DL did the dirty work, guys like Farrior and Clark played smart football and unheralded players like Foote acted as the glue to hold everyone together because, while limited, offered no glaring weaknesses. That combined with LeBeau's coaching and scheme made it a tough unit to contend with.
The offense was the same way with Ben, Ward, Bettis, etc. with a talented OL and just solid football players like Heath Miller with a sound philosophy of playing physical football. It feels like this year's team is slowly building toward a group that has three levels of talent and a clear philosophy on offense, though the defense will still rely a bit too much on the pass rush for success.