Do not underestimate the power of David Prowse!
He was much more than just a tall person wearing a suit! Lesser science fiction movies are full of tall people wearing suits.
Prowse didn’t disappear in the suit, he brought the suit to life. The quick turns. The lean-in. The gestures. And of course the swordplay. It all tells a story.
Prowse moved in a way befitting a Dark Lord of the Sith! A fallen knight who was more machine than man!