re: Why did LSU beat A&M but Bama did not?

Because LSU has a much faster defense and they were able to limit Manziel on the ground. In A&M's two losses this year, Manziel averaged 3.5 and 1.6 yards per carry. In every A&M win this year, Manziel rushed for at least 5.0 yards per carry. Contain Manziel on the ground and you have a good chance of winning the game. If you do not, you're probably going to lose.