Star Wars: The Rise of Skywalker's prequel callback illustrates how similar Palpatine is to Darth Plagueis. One of the most famous scenes in the prequel trilogy comes in Star Wars: Episode III - Revenge of the Sith, where Palpatine tells Anakin Skywalker the story of Darth Plagueis the wise. In the moment, Palpatine's primary concern is planting the seeds for Anakin's eventual turn to the dark side, teaching the young Jedi about the Sith's "unnatural abilities" to cheat death. But the exchange also served as providing Palpatine's backstory, as he studied under Plagueis and killed his master.
Several years later, the Plagueis scene was referenced in The Rise of Skywalker, providing an explanation for how Palpatine survived the events of Return of the Jedi. While the specifics of Palpatine's return were glossed over in the movie (relegated to outside print materials for detailed explanations), it was a fitting nod to the Skywalker saga to hear Palpatine repeat his well-known "unnatural abilities" line. And in doing so, The Rise of Skywalker showed how alike the two Sith are.
The key point of the Plagueis story is he was obsessed with preventing the ones he cared about from dying. While Plagueis ultimately was unable to save himself from death, he did pass these lessons on to Palpatine. The Emperor took great interest in being able to cheat death, channeling his own "unnatural abilities" to stay alive. The Rise of Skywalker novelization reveals Palpatine transferred his consciousness to a clone body on Exegol prior to his apparent death in Return of the Jedi. This shows he had a contingency plan in place in the event of his passing, ensuring he would still be around to conquer the galaxy.
As Palpatine tells Anakin, Darth Plagueis' only fear was losing his power, which is something that can also be applied to Palpatine. He clearly relished his role as the Emperor and wished to rule the galaxy for all eternity. Even at the height of the Empire's reign, Palpatine probably was scheming ways to stay alive. What's interesting is he kept a revolving door of apprentices, always looking to switch before his student attempted to kill him. Count Dooku was a placeholder for Darth Vader, who Palpatine wanted to replace with Luke Skywalker. Even in the sequels, Palpatine started by corrupting Ben Solo and then turned his attention to Rey. He only wanted to conduct with Sith Ritual when he knew Rey, his granddaughter, would be the one taking power, meaning the power would stay in his family.
The similarities between Palpatine and Plagueis highlight a key difference between the Sith and the Jedi. The former are relentless in their pursuit to stay alive and avoid death, clutching on to whatever power they have for as long as possible. In contrast, the Jedi view death as a natural part of life, and willingly become one with the Force when it is time for them to pass. The ultimate irony in the two mindsets is Qui-Gon Jinn seemingly unlocked the key to immortality, teaching Obi-Wan and Yoda how to become Force ghosts.
