When reading Johnson's comments, he had solid reasoning for going to Iowa. He has a point that NU isn't like what we were 25 years ago. Yes, he think/hope Frost can get NU back to near that level, but Iowa has been the more consistent and successful program the past 5 years.
So he wanted to slide into something already consistent, instead of one where he could be a part getting it back to good. Different philosophies for different players.