A symphony conductor is usually a good musician, but seldom a world-class performer. The most effective university deans are often not the best professors. The ability to lead … to Engage Others and to Turn Them On … rarely coincides with being at the tip-top of the … Individual Performance Heap. Which is not to say that leaders shouldn’t have a fingertip familiarity with their particular line of business. But the factors that make you good at the “people stuff” and the “inspirational stuff” and the “profit-making stuff” are quite distinct from the factors that vault you to the Pinnacle of Individual Mastery. In business, alas, it’s all too common to promote the “best” practitioner to the job of leading other practitioners. The best trainer becomes head of the training department. The best account manager becomes head of the sales department. And so on. Tellingly, that’s not how things work in … True Talent Enterprises.
I believe this is called the Peter Principle.
"The Peter Principle is a colloquial principle of hierarchiology, stated as "In a hierarchy every employee tends to rise to his level of incompetence."" [wikipedia]
When I worked in Corporate America, I saw this all the time. After being a Chemist for X Years, he would move up to Lab Manager, with no training or managerial skills (and usually without people skills). Why does this apply here? Because many times, people want to move up the ladder, even when they lack the skills for the next job. This includes you. You may be a great network admin, coder, developer, etc., but managing employees and the minutia of day-to-day operations is not your forte. Few executives realize this. Play to your strengths; hire to your weaknesses.
John Moore has an index to the rest of the book's highlights here.