If we are to believe that Palpatine was in the plan for the ST all along. Then I guess the “Darth Sidious” name-drop in TLJ was very clever on their part.
and also Palpatine’s voice being heard in TFA as well.
(in Rey’s vision - https://www.youtube.com/watch?v=FATqyG8cGSE & https://www.thisisinsider.com/star-wars-reys-vision-explained-2017-7)