Campbell's good. Some of his success came from being in the Big 12 at the right time (when both Texas and Oklahoma weren't that good, and then they left) but it was real success. I think BE is right, he only hasn't been "hot" because he's declined some overtures, but he did try for the USC job. I think when he turned down Notre Dame it was even thought he was holding out for a Big 10 gig. At this point, no, it doesn't matter why they didn't go harder after him sooner, just that they didn't hire anyone at all sooner. Clearly they just assumed Franklin was going to get the guys he got and the decommits were going to decommit regardless.
It wouldn't bother me if they hired an FCS coach or a coach from a smaller FBS school/conference at this point either. All the "big" candidates started out somewhere. If you're willing to hire a coordinator or an NFL guy with only one year of college experience I don't think you need to insist that a sitting HC has to have done it at a place like Iowa State or Memphis or before tackling Penn State. Sure, there's more money and management involved, but coaching is coaching.