The converted a long 4th down to win it. We stopped a short 4th down one yard short to win it. USC was on our ten-yard line with less than a minute to go. Neither us nor MSU really ran away with the game or impressed.
So what's changed since last week, when they were clearly ahead of us. They barely beat a 7-5 team, we barely beat a 4-7 team. How does that have us jump them.
They have 3 wins over P5s with winning records, we have 3 wins over P5s with winning records. We do have a 4th win over Utah State, but it's questionable if they'd have a winning record in a P5 conference. Regardless, the committee doesn't seem to love them, despite them beating up on New Mexico, New Mexico St, UNLV, and Hawaii. Looking at opponents with a winning record is misleading since a lot of our opponents played weaker competition. Utah doesn't get to claim Weber St as a quality win even though Weber finished with a winning record. That's a larger example of the same concept.
So it comes down to wins and losses. Their win (over #2 Michigan) is better than our win (over ~#16 Utah). Their losses are probably better than our losses (@Baylor and @tOSU are similar, but @Purdue is a better loss than home to Boise).
Also, I wouldn't expect the committee to put too much weight on the snow. Snow can favor the run game, but it can also hinder it by limiting the ability of an RB to cut sharply. More than that though, I generally see unusual conditions (whether weather or otherwise) viewed more as a wild-card that can lead to unexpected results.