I've managed sizable groups (in the multi-hundreds) and I fully agree with the above. The manager's job is to enable people to get things done, to eliminate obstacles, obtain resources, and otherwise stay out of the way of the people who know how to do the work. A good manager is in some respects invisible, becoming visible only when the staff need the road cleared for them.
The biggest problem I had was with new line managers, who had to learn that being a manager wasn't about them --- it was about their staff and how they could empower their staff. Being the boss doesn't mean bossing people. As the boss you better know that you work for them because without them you fail.