Motivating and pushing a group of individuals to a collective goal when they have their own aspirations, goals, backgrounds, and skills is a demanding task regardless of the context. Leadership is hard. Difficult choices have to be made, ego has to be handled, and every move needs to be made with the final goal and overall good of the group in mind.
I will never be convinced that any professional hockey team is better or more likely to achieve their goals without the services of Phil Kessel. The Pittsburgh Penguins may be willing to see if that thesis is wrong because according to Josh Yohe of The Athletic, Kessel could be traded due to problems with head coach Mike Sullivan.