We see it all the time in the NFL. An HC is hired based on being a really good DC or OC...... and they fail. Those are different jobs requiring different skills. It works that way in any enterprise. A great middle manager doesn't mean he/she is suited to elevation to upper management.

McVay wasn't hired based on being a great or long time Co-ordinator. He was hired based on possessing the right stuff to be a good HC. Sure; sometimes it happens that a superb Co-ordinator becomes a good HC.

I don't pretend to know if Bienemy, or Saleh, or Staley, or whomever has the right qualifications to be a good HC.

The point is this: there is likely a reason that some excellent Co-ordinators don't ever get hired as HCs. It's not a slight. It's a reality that the owners don't see that person as having the attributes to run the entire team and succeed.