That doesn't mean mid-major coaches can't succeed here. That just means we picked the wrong coach. There have been lots of great successes - do you think Bo Ryan, Matt Painter, or Bruce Weber wouldn't have won here?
Hiring an assistant from a big-time school is a much bigger risk than a mid-major HC, IMO.
Painter played at Purdue, then was a coach at Purdue for one year before taking over.
Bruce Weber was an assistant at Purdue for 18 years.
Bo Ryan was an assistant at Wisconsin for 18 years.
Each of these men had significant experience in a major conference, either playing in one or coaching in one, before they became a coach at a major conference school. In these cases, that experience happened to come in the same conference where they got their head coaching jobs, which is a big plus.
I made a post last year about the Big 12 and Big Ten head coaches. All but a couple of them have major conference playing or coaching experience in their background.
The "big risk" comes in hiring an assistant that has no major conference experience whatsoever. Which is exactly what ISU did when it hired McDermott. It's clear that this lack of experience has hurt McDermott. He didn't understand the talent level required for the Big 12, he doesn't understand the physicality required for the Big 12 (or if he does understand it, he can't communicate it to the players), and it just goes on from there.
If there is a new MBB coach at ISU, and if that coach doesn't have major conference experience somewhere in the resume, whoever hired this coach should be summarily fired.