This is not true tho, is it? If the fans boo and get on the players back the second something goes badly, weather it be because of terrible tactics or bad performances, it will affect moral and therefor the results in the long run, leading to the manager getting sacked if it goes bad enough. If all footballers were psychopaths with no care for peoples opinion, you would be right, but thats not how the world works. The owners dont care about the fans opinions, but they care about results and therefor also moral. Supporters can affect that and therefor also everything that goes with it.