^Exactly! He drains Rey and Kylo to power the Big Sparkly.

I figure that the crystal would just be a way to draw the two most powerful Force users in the galaxy into a trap where they would be either turned or drained, and Rey Palpatine is bait. That the whole Rey Palpatine plot feels so wrong simply feeds into the understanding that it was fabricated by the cultists. Of course, they could have galactic plans for the Palpatine illusion, but once they’ve drawn Rey and the Resistance into their web the galaxy is basically theirs for the taking.

I don’t know how such a plan would be elaborated on unless it was in the scene where Pryde talks to the Palpatine hologram. I suppose that dialogue could be changed with the removal of the Death Star weapons plot to indicate that Pryde is a cultist who is in on the whole thing. Maybe this is the scene that reveals Palpatine to be an illusion, so we know going into the final confrontation that Rey and Kylo are being tricked.