A great hire can change everything for a college football program. A bad hire can destroy it all.
Urban Meyers don't grow on trees. Rarely will a school have a ready-made superstar available and willing to fill their opening. And so yes, Urban Meyer/Jim Harbaugh/Nick Saban are absolute home-runs hires, but that's not the norm.
The reality is most coaches come from the fat part of the curve. Maybe a program swings and misses on their top candidate, but most coaching searches are resolved before progressing to the 4th or 5th choice.
Let's be honest -- a lot of it is luck.