Yes I know it's fantasy but if Luke suddenly made the Emperor vanish by clicking his fingers it would break the rules of the fantasy.
Star Wars treads a line between high fantasy (with magic and fairy folk) and space opera (with people who have alien abilities and interdimensional beings).
A big explosion right next to an occupied planet sized moon still has consequences in the Star Wars universe (it's why Ackbar moves the fleet away before it explodes) you can't move Endor out of the way but you can move the station and having it getting into position to blow up Endor and the fleet parked next to it gives us a reason for it move which adds tension to the story.