Educator Laurence Peter introduced the concept of the Peter principle in his 2009 book of the same name, which has become known by the phrase managers rise to the level of their incompetence. What he’s saying is that people get promoted to a new role based on how they performed in their previous role; however, the abilities required of their new role may be completely different, and possibly ill-suited for them. Eventually, they will be promoted into a role that will not suit them (“the level of their incompetence”), where they will struggle.
