If I'm an AD (or a manager), the baseline I'm looking for is "no heartaches" from my people--they're easy for me to work with, and they meet expectations and don't put problems on my doorstep. There are some ADs that want "their people" but I'd just want people I can rely on and get along with.
Coaches that exceed what I expect are even better.
I also know I can't stand still--NCAA sports are evolving and getting more competitive. My coaches are going to have to be a part of a plan to progress every year so we don't fall behind.
If Key shows that he can win here and looks like he'll improve year over year as we build a program, then he's got several things to his favor--no unnecessary disruption (i.e. continuity, already here), being a known quantity (no unhappy surprises), loyal to the organization.
If I were an AD, I'd wonder "can I get along with him?" and "will he get better year-over-year, or will he plateau as a 6/7-win coach?".
Back in 2003, Ted Roof took over as Interim HC for Carl Franks. Franks had gone 2-5, and Roof went 2-3 the rest of the year, but looked much better than Franks in doing so, and people thought he'd turn that program around. He got the "interim" label taken off. Then, he won 2 games, 1 game, 0 games, and 1 game before getting replaced with Cutcliffe. If you've seen Ed Orgeron as an interim HC, there are very few head coaches who do as well as he does as an interim HC--the problem is, he's a much better interim HC than a non-interim HC. People who saw that don't want a coach that backslides when they get the job "for real"--and that happens in coaching.
The people offering the HC job have to figure out "is the guy I'm going to hire going to do well here?". Even if Key kills it this year, there's still some doubt for the new AD and his hiring team.