Firstly, management and leadership are not the same thing. Giving direction is the job of a leader. Managers, just like anyone else, are rarely good leaders. They are more likely to give the wrong direction and vision than ICs, given that they typically also know less.

IC's do benefit from coordination, as any team might. That is management. However, having more than the absolute minimum of managers and management attached to a product invariably means an exponential decrease in efficiency.

Any team with more managers than senior ICs such as staff engineers is in trouble. That's because staff+ engineers are the people who's ACTUAL job it is to give direction, force multiplication and avoidance of local minima.

Hence, the nature of the position of manager is that it is very often unnecessary, or only intermittently useful. Therefore, a successful manager is not one who makes the product succeed, but rather someone who creates work that they themselves can and need to solve. Typically, this happens when there is a group of managers where there should be only one.