Thinking back to the idea introduced in this film that Palpatine is a conglomerate of all past Sith spirits, perhaps the reason Palpatine created Anakin in the first place, and later Rey, is because he needed a “perfect host” that could contain these spirits and continue to cheat death.

The film already implies that the cloned bodies are quickly decaying because they can’t contain Palpatine’s spirit. Perhaps at this point even a regular person would not be able to contain the Sith for too long. This would explain Palpatine’s decayed appearance even before his death, specially if you interpret the scene in ROTS as Palpatine revealing his true appearance. If you look back at his conversation about Plagueis, he talks about both cheating death and creating life as almost interchangable, so perhaps that was his plan all along. To cheat death by creating a life form strong enough to contain all the Sith spirits without the need for constant essence transfer into new hosts.

And this would explain why Palpatine would see it a priority to create an Anakin replacement as soon as he came back, while he was barely able to hold on to life himself.