If a known quantity like Miles would come to Storrs you grab the guy immediately. If this is viewed as a gateway gig you get the most proven guy because it brings instant credibility and recognition to the table and by definition the gateway gig coach is going to leave for a better situation likely sooner rather than later if he has on-field success. So hiring a guy that has had success in the most competitive league in the land is a no-brainer.
If one of the reasons Diaco got canned was his inability to welcome Kill aboard in an OC capacity imagine what DB would say to the fans if he could that would criticize a Les Miles hire.
Questioning the potential of hiring Les Miles is akin to Fairfield fans complaining that Jim Calhoun was going to be their next hoop coach.