The Peter Principle: promote people out of the jobs they are good at, and eventually management is full of idiots.
No, seriously. Check it out:
At the point where his level of incompetence is reached, an employee’s promotional trajectory usually ends, and he’s stuck in a position where he no longer has confidence in his abilities and produces less work for the company than he did in the position in which he excelled. The problems created by this promotion are compounded by the idea that an incompetent manager will make incompetent decisions — including deciding who to promote. Eventually, says the Peter Principle, the higher levels of a bureaucracy become populated entirely by incompetent people.
And that is all I am going to say about it.