Just to play Snoke’s advocate for a second regarding the consistency in plans: could we potentially assume that Palpatine just didn’t know Rey was his granddaughter in the last two movies? Her first public appearance and the Battle of Crait are only like a week apart, after all. It could have been in the time gap that followed, after she’s shown her strength and Snoke has died, that Palpatine realized who Rey really is, not unlike Palpatine and Vader learning who Luke is between IV and V. Sure, Snoke probed her mind in the throne scene, but he was preoccupied with Luke’s location and died very soon after, and it’s not like her memory was a steel trap considering Kylo mind-linked with her and came away assuming her parents were random drunks.