Rise of Skywalker neither showed nor telled (told). Supposedly the story behind Palpatine coming back was told in a temporary series of missions in the Star Wars Battlefront video game (and Squadrons had some hints in their too if I recall). Of course that was a big failure so now the TV show writers are filling in the blanks because at least they are fans first and money-makers second.

And of course RoS was a giant overreaction to Disney panicking over a vocal minority of perpetually displeased fans didn’t like Star Wars being taken in a new direction in TLJ, so they asked JJ Abrams to take a wet sack of memberberries and turn it into a movie (again).