The Dolphins probably stacked the box and left receivers in less coverage than normal, hoping he'd throw (for the reasons you just stated). My guess is this coming week, the opponent has to plan for his arm and therefore puts more in coverage....so therefore Lamar goes off for over 100 yards rushing and a couple of TD's, and throws for "only" 200 yards and maybe 2 TD's. Double-edged sword, for sure. The Bengals with their nasty pass rush will beat their asses, through. Twice.