You remember when I pitched the idea for TRoS: Ascendant that Rey’s parents should be bad people who abandoned her because she was a Palpatine to preserve the reveal and her arc from TLJ, and you said that Rey needed a motivation in order to be angry so the ritual would work?
Try re-framing it so essence transfer only works if another person kills the subject in general, no anger or dark side or anything like that required. In this version, Palpatine only escapes from the second Death Star because Vader killed his first body. Palpatine hopes to groom Rey so she would be willing to perform the ritual, and once she’s thrown away by her shitty parents he turns to Ben, hoping to groom him so he would be willing to perform the ritual (whereas Luke and Leia are… knowledgeable and thus would be unwilling to perform the ritual). Palpatine is unable to transfer his essence into another body because Rey did not kill him herself, she merely reflected the lightning onto his face.