I'm sure he started with USAID because USAID helped end apartheid in South Africa, something he was a big fan of. Starting with USAID also helps reduce US's power overseas which certain countries would be very grateful for.
He started with USAID because they were investigating Starlink.
He can't touch things like national defense, because that means all his SpaceX and friends' Palantir contracts get exposed for what they are. Cash orders. Once all the smaller hurdles, see CFPB, are out of the way, then the rest of the a16z and Founders Fund clowns will come in with their solution-based ideas shelling their own stupid stocks on how to make America build, dynamic and great. USAID is the lowest-hanging fruit, with everything in plain sight, minimum effort was needed to create maximum distortion. All the peanuts are for him and his gang.
The peanuts don't add up, in this case. The discretionary federal budget is dominated by the military, and the nondiscretionary budget dominates the entire budget.