Ben Solo goes after her, and convinces Palpatine to let Rey live, by allowing Palpatine’s spirit to possess him. As this happens what remains of Ben tells Rey, that it will only be a matter of time before he is consumed, and she should kill him. She does, and Palpatine’s spirit tries to get back to the clone body, but Rey destroys it before he can enter the clone. Being without a vessel for his spirit, the Force ghosts of the Jedi appear, and destroy Palpatine’s spirit.
IIRC this was a pretty popular rumor before the movie came out? Something like this. I know at the least a few people thought the redemption/sacrifice Ben was going to make in the movie was along these lines.
I remember so many people also just kind of automatically assuming there were going to be a ton of force ghosts in the climax once Palpatine got announced. It just seemed to follow that if you were bringing back a long dead bad guy you now had the door open to ALSO bring back all the long dead good guys as a counter.
I think the issue wasn’t just bringing back Palpatine, but by extension killing him again. How are you going to convince people he’s really gone this time? I don’t think blocking some lightning, whilst saying “I’m all the Jedi” was very convincing. For all we know he has clones waiting for him all over the galaxy. The entire concept of his return just wasn’t properly thought out beyond some flashy action sequences.