Somehow, Palpatine returned. He nearly returned much earlier in a different kind of story.
The actor behind the Emperor, Ian McDiarmid, has spoken about a conversation he once had with George Lucas about some plans for the character, specifically a show centred around him.

IGN reported from SpaceCon 2026 in San Antonio, where McDiarmid revealed what was discussed.
Lucas pitched to him the idea of starring in a project that would have followed Sheev Palpatine’s rise to power, paralleling that of Hitler.
“[Lucas] was talking about, I think I can tell you now, a television series. We had lunch one day, and he said ‘I’ve got this idea, and I hope you might want to be involved.
We could sort of follow the Emperor’s progress, like Hitler’s, some of that. There might be an assassination attempt, and of course it wouldn’t succeed.’ It sounded really exciting, and he also said that maybe you could direct one, and then I fainted. But sadly, that didn’t come to pass.”
Andor told the story of how the Empire strengthened its grip on the Republic directly before the events of Rogue One, telling adult focussed stories about the nature of politics and power.
It may have done it better than this proposed version, keeping Palpatine very firmly in the background.