Why do the hard work of actually trying to maintain power when you get all the trappings of a respected position and can do whatever you want and still have power?

Because you don't get those things if you don't try to maintain power. You don't rise to the pinnacle of the American legal field if you're not ambitious and driven and have a strong desire to get to make these decisions.
You want to be the one who makes these calls. You want to be in the room where it happens, to coin a phrase.

If you let Donald Trump become a dictator, you don't have any power any more. You don't have a respected position any more. You're just a figurehead, making about the same salary as a fourth year lawyer in a BigLaw firm. Right now, even the President of the United States has to listen to what the Court says - and they do. Every President loses several cases before the Court, and has to abide by their rulings. That goes away if you give up the power of the Court.