I just mean that the sheer power of the Sith spirits makes it more plausible he could survive being thrown down a shaft and blowing up, it’s a revelation that he’s even more powerful than we knew, so we can digest that he could come back after we thought he was defeated.

Also the idea is the spirts of the Sith were transfered to him when he killed Plagueis, it builds on the idea of the Rule of Two and the fact the apprentice is always trying to overtake his Master, revealing that this actually passes down their essence, building up their power through the generations, it’s so unnatural, selfish, and right in line with the Sith. It adds a new layer to the character in the previous movies and it’s in line with the “pure evil” persona Palpatine was always seen as. And as I said it gives a much needed finality to the final film in the saga to have the Jedi banish the Sith once and for all.

When I say it’s the only thing that justifies Palpatine’s return in this trilogy, I mean that the character had no reason to appear, he had absolutely no part in the story that this trilogy had told so far. Making his character “The Sith” at least plays into the broader conflict that spans way back than even the prequels and makes it feel like a deifinive conclusion.