Of course, that was because he was amped by Rey and Kylo's power though.
Was him calling on the power of all the sith implied to be a new power? The novelization states that he called on the power of all the sith when he draws Kylo and Rey's power from them. I'm just trying to figure out if he's always had that power, if it's because he holds the spirits of all the sith, or if it's because he is on Exegol (a possible dark side nexus)
I don't think there are any statements in canon which explicitly state that Palpatine's power had grown in the time between RotS and RotJ... But given the fact that he had an abundance of knowledge that he was hoarding/studying over this time, we can logically infer that RotJ Palpatine > RotS Palpatine.
"I am tired of Earth. These people.
I am tired of being caught in the tangle of their lives."