In Revenge of the Sith, we see Darth Sidious seemingly deformed by his own deflected Force lighting. Right off the bat, this is by far the most popular and likely explanation for his appearance.
Windu eventually gets the better of Palpatine before deflecting his Force Lightning back against him, which appears to twist and melt Palpatine's face as his body begins to smoke, turning him into the grotesque embodiment of the Sith that acts as the final antagonist for both Star Wars: Episode VI - Return of the Jedi ...
In the novelization of The Rise of Skywalker, Kylo Ren deduced that Palpatine's dark side spirit and power were too strong for the clone body to handle, causing major deterioration, which is known to happen to many dark side users – the stronger they get, the more damage to their physical bodies.
After quickly dispatching three Jedi Masters, in ROTS, Palpatine is left facing Mace Windu alone in a duel. Windu disarms Sidious, and the Sith Lord resorts to using Force-lightning agains this foe. The lightning is redirected back to its user by Windu's blade, and a lot of it ends up on Palps' face.
As one immersed oneself deeper within the dark side of the Force, its malevolent power took a toll on the body.” ^^Also yes, “Darth Bane explained that the reason for this physical degradation was because flesh and bone lacked the endurance to channel the immense power of the dark side indefinitely.
He understood he lost the ethereal battle before their physical fight even began. Thus, Palpatine never viewed Yoda as a major concern, even though the Jedi Master fought him to a de facto draw during the events of Revenge of the Sith.
There have been various reasons for this very briefly touched on in expanded universe offerings. One reason being that the clones were too expensive to produce and raise. Another being that getting citizens to sign up to fight for the Empire made those same citizens and their families more loyal to the Empire.
Summary. Some dark siders can conceal their appearance with the Force, hiding physical signs of corruption like yellow eyes and aged features. Palpatine's yellow Sith eyes may have been hidden through a dark side illusion, potentially masking his true form from the Jedi.
As a new episode of The Bad Batch Season 3 reveals, Palpatine's biggest mistake was rallying and urging on the Separatists during the Clone Wars. Sure, it threw the Republic into chaos and helped him seize power, but it also helped inspire the very Rebel Alliance that brought him down.
Years after his death, during her duel with Jacen Solo, Lumiya alluded to Palpatine, saying he was a "psychopath consumed by power.". Palpatine's manipulative behaviour cannot be exaggerated as he manipulated the entire galaxy into doing his bidding.
As the Death Star had been destroyed, and the Battle of Yavin had finally taken place, the years then moved into ABY (After the Battle of Yavin). It's said that Star Wars: Return of the Jedi takes place during 4 ABY, meaning Palpatine was 88 when he met his original end.
Palpatine carried the lightsaber for a great deal of his life afterward, though he only rarely wielded it in combat, as his position as Emperor made battles with other Force-users few and far between, and he preferred to rely on his raw ability with the Force in any case.
Yoda struck the Podium too hard to control his landing, and he rolled off the main portion to the edge where he desperately attempted to climb back up. His hold on the smooth edge failing, Yoda lost his grip and fell several stories to the floor. Yoda chose to retreat as Sidious cackled in triumph above him.
Order, in his eyes, Yoda and the Jedi no longer posed a threat to his role. during the early years of the Empire, Palpatine only sent Vader to hunt survivors. in order to strengthen his hold on the X Jedi. and to corrupt his apprentice.
Some believe this is part of the evidence for the Force Mask theory. Although, it's probably because all Sith's eyes turn yellow through the Dark Side of the Force, in which Palpatine released when using Force Lightning. He WAS a former Jedi.
In Legends, it was suggested that Palpatine used a Sith power known as "Mask" to hide his true face, suggesting the lightning did not cause his disfigurement. Instead, the lightning only broke the spell and revealed the Sith Lord's true appearance.
Palpatine understood the history of the galaxy as a constant war between the dark side and the light, embodied by the Sith and the Jedi. He sought to bring about the ultimate triumph of the Sith, extinguishing all trace of the light.
According to Imperial Estimates in Star Wars Inside #87, only about 100 of the Jedi survived Order 66. Most were subsequently hunted down and killed in the years following the Great Jedi Purge.
