Disney has been rather clear that it has returned Sheev Palpatine to the Star Wars saga in Star Wars: The Rise of Skywalker.
It’s important to remember a key scene from Star Wars: Episode III – Revenge of the Sith.
During an opera, Palpatine tells Anakin Skywalker about the Tragedy of Darth Plagueis the Wise. Anakin learns that Plagueis knew how to prevent death and that he taught his apprentice everything he knew.
Current, Disney-owned canon has confirmed that the apprentice was Palpatine, also known as Darth Sidious.
(That canon is the book Tarkin.)
For these reasons, it seems clear that Sidious is back because of the power of Plagueis.
The questions remaining is how this power going forward in The Rise of Skywalker will be expressed and manifest, or how Palpatine will utilize this ability.
The supposed leaks of the plot are that Sidious is utilizing living beings to restore life (and power) to himself – those beings being Rey and Kylo Ren.
(Particularly, Palpatine is draining life force through something called a Force Dyad. (That’s Rey and Kylo together, each representing the positive and negative sides of the Force, respectively.) That gives Sidious new vitality. Also, the Swedish Cinema Department mentioned: “a frightening man who draws the life force out of people.”)
True, influencing midi-chlorians to create life, as Palpatine talks about at the opera, and tapping into the Force Dyad are not the same. But is the latter an extension of the powers to create life that Plagueis taught Sidious?
(Also, did Palpatine use the power of Plagueis to create dark side Reys, as Palpatine created Anakin?)
We’ll find out soon enough. The Rise of Skywalker hits theaters Friday.