The loss of offensive composure did.
For a team that prided itself on not turning the ball over throughout the season, the Steelers were giving it away in the Super Bowl like it was a three-for-one sale at Joseph A. Banks.
In fact, the Steelers did turn the ball over three times but did not get one back from the Packers, and that's a death knell in the Super Bowl.
Teams that turn the ball over less are now 33-3 in the championship game. That overrides a trend that saw the team with more rushing yards going 36-8 coming into this game. Those teams are now 36-9 after the Steelers outrushed the Packers 126-50 and still lost.
"Usually when you lose it's because of penalties and turnovers," said Steelers coach Mike Tomlin, and he was right.
On the Steelers' next possession, trailing 7-0, Roethlisberger was hit by Howard Green and threw a wobbly pass that was intercepted by Nick Collins and returned 37 yards for a touchdown and a 14-0 lead. And for those following trends, teams that return interceptions for touchdowns are now 11-0 in Super Bowls.
Even though Roethlisberger was intercepted again two possessions later by throwing into double coverage, and the Packers' lead had reached 21-3, the Steelers still had a golden opportunity to win.
After cutting the deficit to 21-17, the Steelers had the ball first-and-10 at the Green Bay 29. But a batted pass was followed by a completion to Heath Miller that lost three yards, and then Roethlisberger was sacked on third down. A 52-yard field goal attempt by Shaun Suisham was well off the mark, and Tomlin called it a bad decision on his part.
"It was a terrible decision," Tomlin said. "It wasn't even close. But we made the kick in pre-game and he had kicked the ball off so well going in that direction. I took that into account and we took a shot at it and failed."
The Steelers still had another chance to take the lead as the fourth quarter began. But on second-and-2 at the Green Bay 33, Rashard Mendenhall fumbled for the Steelers' third turnover. The Packers then pushed the lead back up to 28-17 with 12:03 left.
Roethlisberger drove the Steelers for a touchdown and two-point conversion, but he couldn't bring them all the way back this time.
A special-teams penalty by Keyaron Fox set up the Steelers' final possession at their own 13 with 1:59 left. Roethlisberger moved the chains once, but on fourth-and-5 threw a high pass to Mike Wallace and the Steelers' dream for a seventh Lombardi Trophy came to an end.
Roethlisberger finished the game with 263 yards passing and a pair of touchdowns to go with the two interceptions for a passer rating of 77.4.
"It was a tough game and there were probably a lot of what-ifs," said Roethlisberger. "There were a lot of throws I'd like to have back. I don't put blame on anybody but myself. I feel I let the city of Pittsburgh down, the fans, my coaches, my teammates. It's not a good feeling."
Tomlin was asked about Roethlisberger's performance and said, "It was a losing one – just like mine.
"They made plays, guys," Tomlin continued. "It was probably less about what we were unable to do and more about what they were able to do. Such is the case in the greatest game, in this game. We can sit here and make excuses, or you can. I will not. Green Bay played a really good football game, man, and made the necessary plays to be world champs."