Difficult question to answer!! No easy - quick answer so I'll just throw in a couple of thoughts.
ATC is a fast-moving, constantly changing world. The Manager needs the ability to look ahead, consult with staff and encourage their ideas, plan for change and manage it effectively.
Unfortunately, many people appointed to management start creating change just to try to impress their superiors. There has to be a genuine need to make a change such as improving safety etc.