Weis was a fool to waste time with the spread option. No one disputes that. But Jones was 3rd on the depth chart for the "real" offense, and the fact that Kelly moved him to Linebacker and never had any interest in letting him try Q.B. afterwards speaks volumes about his talent for the position.
Further, the guy quietly enrolled at Northern Illinois, then practiced all week afterwards as the starter for Michigan, and then snuck out of the program the night before the team loaded the bus to head to Ann Arbor.
And then later, he was such a headcase that Butch Jones wanted nothing more to do with the guy and ran him off.
Weis is responsible for plenty of failures. Demetrius Jones' failure is not one of them.