I think Palpatine preferred just taking a new host, whether it be Rey and Kylo. He asked Kylo to kill her, and he figured whoever survived the encounter would be the most worthy host.
I guess the Dyad thing doesn’t necessarily equate to the rising and falling of the dark side and the light that we see personified by the Jedi Order, then Vader/Palpatine, then Luke, then Kylo, then Rey. Somehow, Kylo realized they were a Dyad offscreen at some point independent of Snoke, and Palpatine didn’t realize their connection was a “Dyad”-level connection until they were together.
It’s just dumb because the Dyad is never really explained outside of what Palpatine says at the very end of the film. We don’t even learn how Kylo knows they’re a dyad. I would almost suggest cutting the term to just not add to the confusion, but I feel like that specialness is necessary to explain how Palpatine can just drink Rey and Kylo’s Dyad Milkshake and get that Sith sugar rush.
Jarbear, I didn’t really take it as one bad guy rises, another good guy rises. I just took it as an interpretation of the way peace and conflict wane and wax naturally overtime. Darkness rises, and light to meet it.