Why do people think an AD needs to be fired if one of his hires doesn't pan out? Does your company fire it's HR manager every time one of his/her hires doesn't work out? Of course not.
The whinging on this board is reaching epic proportions.
The difference is in magnitude and weight. You're suggesting an HR manager making "one of his/her hires", and it turning out poorly, is the equivalent of an athletic director hiring the head football coach at one of the most storied, respected, and well-funded football programs in the country, and that hire not turning out.
Very different circumstances. You could make a list of the most important jobs in this state and NU's head football coach would be Top 5. That's not a place you can make a hire and casually not let it "work out."
The AD's number one job at the University of Nebraska is the sustained success of the football program, and that means having the right head coach in place. The baseball, basketball
and volleyball programs are nice, but they're not what makes the department tick.