Unfortunately what seems to happen is that the better coaches get other (better) jobs and leave while the poor coaches nobody wants and you're stuck with them until you decide to cut your losses and replace them.
It happens in all workplaces.
It's why the union idea of open redundancies is a disaster for workplaces.
The good staff can see the writing on the wall and get another job, improving and energizing their next workplace.
The duds can see the writing on the wall and cling like barnacles, usually playing politics, sucking productive life out of a dying workplace.
