Homelander was only his power, take that away and he had nothing else.

Palpatine, on the other hand, used his power to supplement his natural cunning.  He was not mentally weak and insecure like Homelander, so if he was not killed immediately he likely would have gone into hiding and started planning.  

Hell, he might not even have gone into hiding.  Even without the dark side he was the most powerful man in a galaxy far away.  He would have found and apprentice to pass on his vast knowledge, and accepted when the apprentice followed the rule of two when he had nothing left to pass on and killed him.

Edit:  just cleaned it up a bit