T H E R E B I R T H
Shortly after the return of Palpatine it became increasingly obvious to those around him that his clones were unstable.
Aging at an immensely accelerated rate, Palpatine went through several cloned bodies before his chief doctor informed him of a serious problem:
the clones were contaminated and no longer viable. Panicking, Palpatine went to Korriban, to seek counsel from the dead Sith Lords.
Initially they proposed him joining them in the crypt, to live forever in the Dark Side. Palpatine however, would have none of that.
He had read the ancient Sith texts and knew them all too well. The Dark Side did in fact hold the secrets to eternal life.
The dead Sith Lords told him to seek out an unborn jedi and to transfer his consciousness into it.