I think it was a "different" team this past Saturday than the one of the previous 4 games. The team this past Saturday was extremely tentative and passive for nearly the first two quarters. The team this past Saturday was dropping catches that they were making in those previous games. The team this past Saturday was very undisciplined on defense for the first half. Passive play calling...like the choice to not go for a TD in 4th quarter.
I do agree that ISU has a small margin for error. In October, the errors were minimized. That wasn't the case on Saturday. Maybe it was listening too much to the media reports about how bad WVU was on defense, or how WVU was banged up on offense, or putting too much credence in ISU's top 15 ranking. It seemed to me that the mental preparation wasn't there, and the intensity level didn't come back up until it was too late.
Regarding the passing game...Saturday (and this has been commented on in other threads), there were several occasions where WVU corners were backing off the receivers at the snap (leaving a big cushion). ISU has to make them pay for that. Instead, many times passes were thrown into a rather "busy" middle of the field. I don't know if that is the QB missing a read, or the offense just doesn't have audible of some kind to deal with that scenario.