I think the time to prepare is irrelevant. Even though Iowa had a month to prepare they still aren't able to simulate what they do in practice. Iowa doesn't have the athletes or the knowledge/experience to simulate GT's offense in practice. You can look at tape for a year but if you can't duplicate it in practice it doesn't matter.
On ESPN's college football show last night after the game analyst Trevor Matich said that the preparation time was overrated. He said that Iowa played the same way they have all season. Iowa just playes solid disciplined defense. Nothing flashy and nothing different than they've done all season.
Having Clayborn didn't hurt either. How many D-ends can shed blockers and attack the ball like he did last night. Iowa's defense was simply a good match (or bad, depending on the side your on) for GT's offense. Good D-ends and linebackers are no match for that offense.