The reason Henry was going to hard in the first half is because of how active Lamar was pulling the ball and running.  

They ran primarily to the left because Lamar is right handed. So there's a threat to run that holds the LBs on the backside.

Lamar's pass threat keeps the Safeties from vacating the 3rd level immediately. 

When they are under center, the run game is so much easier to defend because they are back to 10 on 11.