1) Saint Louis' defense is terrible as the 1st half proved.
2) Teams that allow 40 points in the previous game, as Houston did, cover at a good clip in the following game (improved focus).
3) The Rams ran for 6 YARDS in week 11 against a weak Ariz D.

The StL middle linebacker made an incredible INT on the Saint Louis 10 early in the 2nd half to prevent another Texans score. Without that play, I don't think Saint Louis has any chance to win this game or send it to OT and maybe we wouldn't be having this conversation (although I think it's important anyway). Lots and lots of things fell into place for StL to cover.

I don't regret this play regardless of the result.

Edit: And lastly, the Texans playing in front of their home crowd is usually strong enough motivation for any team to play its best. I think it's silly to argue teams have little motivation to win without playoff hopes. These are careers on the line every Sunday.