Camille Fournier:

Either way, it is important to realize that these more senior levels are not a measure of betterness, or quality, or raw intelligence and technical skills. They are instead a measure of demonstrated impact and confidence in the scope of work that the person can be tasked to accomplish. The people who get these promotions are trusted to navigate the systems of the company, to understand what is valued by the people around them and where to spend their time, because they have done just that.