I always assumed that Palpatine looked old and horrible in Jedi because he was already 80 years old in the prequels, and Return of the Jedi was almost 30 years later. I guess it’s because his face melted though.
That was something they fucked up. Realistically they could have gone one of two ways with it.
A) He’s already very old in the PT so in the OT he’s wrinkly cause the dark side has kept him alive past his expiration date. It seems like they were going this way in AOTC where Palps is on his way towards wrinkly (but then they dialed in back in ROTS - where he looks much younger - and necessitated the big wrinkly transformation).
B) The wrinkly is his true form which he is hiding. In fairness to ROTS, this is a legitimate interpretation of what happened.
But what ROTS really seems to be showing is that Palps turned wrinkly because he got hit with his own lighting. Or wait maybe it was because he was going crazy with the power of the dark side? I’m not sure. Did George even know what that was all about?
Either way, the real travesty of it all was the atrocious ROTS make up.