Palpatine is congratulating his faithful on how well they succeeded in resurrecting his body, by cloning.

Clones are obviously made, so this line justifies the claim that he is a clone.

There’s a generous reading of Palpatine’s “Look what you have made” quip in The Rise of Skywalker: ‘Look what you have made.’ This line is spoken by Palpatine just after he absorbs Rey and Ben’s life energy. That giant stone monument that floated above Palpatine’s chambers has to be used for something, after all. Secondly, it suggests they have resources far beyond what is shown in the film. First, they have cloning technology advanced enough to make several replicas of the same individual. The presence of many 'pickle Snokes' in the holding tanks demonstrates two facts about the Sith cultists on Exegol. Remember those creepy baby Snokes that were bred on the Sith planet Exegol? The Reddit user says that proves that the Sith had cloning technology: Snoke. Check out the full breakdown if you want to see every nod the films make, but here are some highlights. Turns out there are a handful of easter eggs buried throughout the series, dating all the way back to Episode III: Revenge of the Sith. There are some Star Wars novelizations that give some more details on this, but what about the movies? This week, a Reddit user went on a deep dive of the Skywalker Saga, hunting for any kind of precedence the films could’ve set for a Palpatine clone. And Rey’s father, too, was a Palpatine clone, only the job was botched. Star Wars gave a very Westworld answer: He was a clone! Makes total sense. A 'Star Wars' Theory Says Palpatine's Plan Worked

Why did the empire not use clones