I will bet you five bucks that the Cardinals will win the Superbowl because the Steelers will have partied too hard the night before. The coach for the Cardinals has the team locked down while the Steelers were allowed to go party.
Maybe they shouldn't have been there according to you, but they were and thats all that counts. Luck is a part of every game, and every team will take all they can get. I'm not a Cardinals fan but if they weren't supposed to be there then who was? Some team that they beat? Its all about points on the board, however you can get them. And this was a great football game.
The Cardinals had 8 wins. The only reason they were there is the divisional layout, and the requirement to take the winner of each division.
NE, for example, had 11 wins, and gave the Cardinals a 30+ point beating at the end of the season, and didn't make it.
I'm not saying they need to change the format; I believe it is in place to keep interest up around the country geographically during the playoffs. And this is a rare situation where teams with much better records don't go, and .500 teams do. But, it can happen and this year it did.