At Star Wars Celebration last year, when it was first revealed that Sheev Palpatine would be returning in The Rise of Skywalker, Lucasfilm President Kathy Kennedy said that the idea had been in the works for a long time.
Apparently a recent interview that Roger Guyett, the film’s visual effects supervisor, did with Cinefex revealed that J.J. Abrams originally wanted to bring Palpatine back in The Force Awakens:
“[Actor] Ian [McDiarmid] was such a major part of the original films. J.J. wanted to bring him back to reveal that Palpatine wasn’t completely destroyed in Episode VII. He created a clone of himself and, with the help of Sith loyalists, rebuilt himself to a fragmented and unstable state. When Kylo meets him, Palpatine is not fully formed, and he relies on tubes and mechanics, moving around this Sith laboratory on a mechanism that Kevin Jenkins designed. He has the spirit of the Sith, but he’s trapped inside a body that’s incomplete.”
Guyett was the visual effects supervisor for both The Force Awakens and The Rise of Skywalker, as well as Revenge of the Sith. So he worked with Abrams on both the start and finish of the sequel trilogy, and therefore it’s very interesting what he has to say here, because he would certainly know.
One important consideration to keep in mind is that we don’t know how far into the development process Abrams wanted to bring Palpatine back. It obviously didn’t make it into the final cut of the film, and we’ve had no indication that it was in any significant version of the film either. Its most probable that it was an idea floated around at some point earlier in the development that was entertained before originally going in a new direction.
But with Abrams returning to the franchise for TROS, he saw an opportunity to pick back up on that idea (just like he did with the idea of returning to the Death Star ruins, another idea entertained for TFA). So in that film he did bring back Palpatine, who was a clone of himself working with the Sith Loyalists. It seems then that Abrams just returned to that idea.
So whether or not that was ever the intended end point, and whether or not Rian Johnson was working toward that end, it doesn’t seem like Abrams’s decision to bring back Sheev was random or sudden. And therefore it fits with what Kathy Kennedy said at Celebration, that it was in the works for a long time.