Clemson went in an unorthodox direction with Elliot. He didn't have the "resume" that guys like O'Brien (Bama) and Wilson (OSU) have. He had little experience before coming to Clemson, and only had three years as a RB coach at Clemson. Despite his lack of top-level experience, he turned out to be a home-run hire as OC.
You gave three examples. Elliot was one of them. He doesn't fit the "hired because of a great resume" model. Does that mean Rees will win a Broyles Award? No. Of course not. It just means "hired because of a great resume" doesn't appear to be the only model, even for the likes of elite Clemson.