How many of those offered him as a quarterback? You say Kirk Ferentz lied to him, I fail to see how he did that. He told him he would be given the opportunity to play quarterback, he was given that opportunity and was going to get beat out by a younger player. You expect a recruit to expect that he's going to fail?
Also, you bring up KSU, but you do so knowing what you know now. KSU wasn't very good in 2009 and was trending downward (it might have been the year they fired their coach even). With Derby signing in February of 2010 that makes a pretty big difference.
I'm sure there were other programs willing to give him a shot as a QB and any of them with a history of using running QBs would have been a better fit. He was dumb for assuming he would fit the mold for an Iowa QB or he was dumb to assume they would change their scheme to fit him.
It's like expecting Tebow to turn into Tom Brady. Not going to happen and Tebow would have no chance to fit into the NE offense.
KF didn't lie by saying he would get a shot to play QB, but I sincerely doubt he was honest about his chances of making it as a QB. It was a promise made to a lifetime Hawk to get him on campus and then move him where they saw fit. Even Tom Kakert flat out said that AJ Derby would end up at TE or on defense, and that was before they signed him.
AJ was fooling himself.