They all have to win two games instead of one. MSU is above OU because they won a conference title game, seems that not having a title game has impacted the Big 12 again.
MSU being a bye is a bit harsh. They beat tOSU, Oregon, and an undefeated Iowa who was going to the playoff themselves if they won the game. Their only loss was on a BS call at Nebraska, on top of all of that. They certainly aren't pretty, but they win games. Maybe Alabama steam rolls them, but for MSU, playing Bama is probably the best opponent of the 3.
Oklahoma has certainly impressed, but they lost to Texas. And, again, they didn't play in a conference championship game. I'm not saying I agree with any of it, but it seems that they were penalized for not having that conference title game.