Too many cooks spoil the broth

Although many hands make light work there should be only one cook in a kitchen. If there are several of them they will disagree with each other, get in each other’s way, put too much salt in this and too much pepper in that, and spoil not only the soup but probably the whole meal also.

The same thing applies to most other enterprises. If too many people try to do the same thing at the same time, chaos, will reign.