You do understand that the idea is to make the best college team right? And ISU did better defensively against common opponents than all but Michigan on that list.
We played Minnesota and Penn State at home and not on a rain wrecked field.
Iowa shot themselves in the foot too many times in Ames, dropping a TD and settling for a field goal on a 4th and short inside the 10 when a QB sneak was guaranteed as demonstrated later in the game when Linderbaum pancaked Lima. Also missing Jackson didn't help.
I watched all those games and I wouldn't take ISU's defensive front over any of those. They were all top 25 scoring defenses for a reason.