Star Wars: The Rise of Skywalker brings back the main villain of the saga, Emperor Palpatine. Their return in Episode IX was heavily criticized because the whys were barely explained, but also because they changed the official canon. It is already known, the theory of the chosen one, that Anakin Skywalker embodied and that said that he would bring balance by force. More details have now been provided about Rey’s fit within those Machiavellian plans.
The former Emperor Palpatine had been hatching his plan for the past thirty years. Hidden on the Sith planet Exegol, the original intention was take advantage of the influence the dark side had on Kylo Ren to make it the receptacle of his future as the new ruler of the Galactic Empire. It’s not likely that Palpatine considered it an equal treatment, so chances are that sooner or later he will end up taking full control. Anyway, before his flirtations with the light, Sidious then noticed his granddaughter.
One more piece of information for the puzzle
The Secrets of the Sith book tries to stitch together some of the inconsistencies in Star Wars: The Rise of Skywalker and reveals that Palpatine had to adapt to the circumstances and events that were taking place, so he modified his initial plan. Because, It was Darth Sidious himself who sent the young woman the image of the Dark King in the Throne Room of the ramshackle Death Star. He intended, naturally, to lure her to the dark side.
At the end of The Rise of Skywalker, Rey and Ben Solo (Kylo Ren) arrive at Exogol and confront Palpatine. It is then that the old politician and Sith in the shadows until Order 66 offers his granddaughter the throne, through a procedure in which he is must assassinate him using hatred. And you know, fear and hatred are a direct ticket to succumbing to the dark side of the force. So many years of preparation end up on paper, because Rey does not fall into the trap and chooses the light side. And they were happy and they ate partridges. Well, partially.
Source | Screenrant