Palantir goes to the agency and says, "Give us data and we'll give you "actionable intelligence".
You know, back in the 90s and early 2000s, the term "data mining" was perjorative. Financial operators would look through their mass of data for correlations and sell them to people who would discover that they didn't actually work.
1) yes, the LE do already have the data.
2) agencies don't 'give' data to palantir, law enforcement data almost always lives in air-gapped environments it cannot leave in any way (or only in highly restricted ways)
3) we don't 'give' actionable intelligence, we just provide tools for analysts to generate such data. Palantir is a company of software engineers, not of intelligence analysts.