The owners shouldn't be hiring successful coordinators, they should be hiring successful leaders. Often, those will coordinators, but they don't have to be.
The skill set for a HC is very different from that of a coordinator. That is why most fail. I actually think McDermott does have the right skill set to be a HC. The fact that he is also a good coordinator is great. But you can't replace the role of a HC with that of a coordinator. Someone needs to fill that role. And being a HC and a coordinator is asking a lot. Some can pull it off, some can't.