I got to thinking about the Star Wars trilogy lately and the shape of the plot, and it hit me full force that there's one single moment that's the climax of the entire 6+ hour series: Luke switches off his lightsaber. (Clip @ Luke Confronts The Emperor: https://youtu.be/PqaiKmm8gsY
The real battle was inside Luke all along.
There were prophecies that a Chosen One would "bring balance to the force". Luke's inner strength inverted the entire power dynamic across the galaxies.
Emperor Palpatine's plan all along was to sacrifice Vader to bring Luke to the Dark Side. Moments ago he said:
"Fulfill your destiny and take your father's place at my side."
Only a powerful act of hate could fulfill a Jedi's path to the Dark Side. I don't think Palpatine planned to step in at the last moment and save Vader. Luke's process of embracing the Dark Side would have been interrupted. His plan was for Vader to die. That suggests he acknowledged Luke as the stronger ally.
In the final desperate moment, Luke didn't even try to run. Either he knew it was hopeless, underestimated Palpatine, or something more. Maybe he expected to die and that just couldn't shake his resolve. Maybe he trusted Vader to turn and protect him.
Luke's courage had overcome The Emperor, so much so that The Emperor forfeited, acknowledged he would never be able to turn Luke, and decided to kill him instead. Was he now so afraid of Luke he wanted him eliminated? Was he intending to prove a point to Vader and solidify his dedication to the Dark Side?
Whatever he had planned, it was too late. Luke's courage and trust had won over Vader. Now Palpatine was lost. He couldn't take two Skywalkers, even wounded as they were.
This was a pivotal moment in American cinema and pop culture, but it happens so quick it's easy to breeze through and miss all the emotional dynamics. There really is much more to the original Star Wars trilogy than lasers and spaceships.