Today I am asked about X. I say "You know the Peter Principle"?
This answer was more an amusing way to explain a deeper issue, and not really what I thought about X.
Although the Peter Princple says "in a hierarchy every employee tends to rise to his level of incompetence", the real story is we all grow past some of our competence zones, but we also build some new ones. A key competence for managers to aquire is to have enough confidence to pull their ego back, and let others shine; It is to understand that management is about helping others to succeed.
Highly skilled employees that are given management positions will fail or succeed on their ability to understand that it is not "about them", but about the project and the people they are asked to manage.