The problem is though, that the possession concept itself is shit. If killing Palpy allows him to possess you, the writers have created a no-win scenario. At that point, the only option for resolving anything is to gloss over the idea entirely. Rey decides that she’ll let Palpy take her over (because that will somehow allow her to control the fleet, even though Palpatine will be the one in control?), but then she senses Ben, and is like “Well shoot, what am I doing? This is a terrible idea!” But then as soon as Ben joins her, they’re about to kill him together anyway. And then Rey ends up killing Palpatine, but he doesn’t possess anyone. He just dies.
You have to kill him with the dark side in order to be possessed. And thankfully the Force ghosts we added in serve a purpose beyond fan service: they hold Palpatine’s spirit in place so it’s finally destroyed.
There are ways for it all to make sense, but unfortunately the writers didn’t take the time to think about them. I could explain more of what they are, but whatever.