The same way a DIII coach translates to ISU: it really doesn't. Everything about this is a risk, and it all operates under assumptions and perfect scenarios. Sure, Leipold knows what it feels like to win, a lot, at DIII level. Frost knows what it's like to win, a lot, at a P5 school. Ultimately, they both know how to win, they just got there differently.
Not having HC experience doesn't disqualify them as a potential candidate, just as having HC experience doesn't necessarily mean they won't suck a** as an ISU head coach. It's all completely unpredictable.