I watched the game replay. Earlier someone mentioned that the Rams dominated in the trenches / won the line of scrimage. To me, it seemed that the Rams imposed their will on the 9ers during the 4th. The 9ers, especially their offense, seemed to get weaker and more inept as time rolled on.
I noticed many 9er fans are really hating Jimmy G and blaming him for the loss. After watching his performance during those last few downs I could see their point. Personally I don't think he's that bad, but he seemed to unravel during that time. His chucking of the ball as he was being sacked looked very similar to Kyler's chucking of the ball that was returned for a TD.