What makes Beamer so scary? He's coached under some of the best the game had, and has, to offer. Fulmer, Spurrier, his father Frank, Smart, and now Riley. He's basically been groomed his whole life to be a head coach. He knows the Southeast extremely well, and he's obviously familiar with USC.
Dabo was not a coordinator or head coach prior to his hiring. Sam Pittman is doing well at Arkansas right now and was never a coordinator or head coach either. I think you're underselling the title of assistant head coach honestly. I'm a firm believer that Shane will make a great head coach in the very near future.