In my mind it would probably look like a bell curve where, out of about 350 D1 programs, you'd have 25 great coaches, 100 good coaches, 100 average coaches, 100 bad coaches, and 25 terrible coaches.
I don't have an analysis of former BYU coaches, but we can definitely all agree that Henry Rose was great (he went a perfect 8-0 during the 1910-1911 season!)