Lawfag here. This may be 4D chess. The U.S. Attorneys were all appointed by Trump, and they do their own hiring for each office, located all throughout the country. Safe to assume the career DOJ lawyers in DC are very swampy. But the U.S. Attorneys' offices reflect their districts. A prosecutor in western Nebraska or South Dakota may be more pro-Trump than the careerists.
Also, U.S. Attorneys' offices aren't all prosecutors. They have civil lawyers who would be very experienced at document review.