Comment by scarab92
Not really, agencies are merged and split and have their remit changed all the time.
If there were a way to efficiently manage 2.5 million staff in a single department, then we'd likely do that, but it's more efficient to specialise, so we do that instead.
Firewalling data between departments is rarely a design consideration, except in obvious cases (military), and it hardly matters in this scenario anyway, because it's not like Musk is walking into all 400 agencies with a laptop. DOGE is hiring an army of advisors and dividing them up between agencies.
I don't know about the US but in other countries it is definitely by design that the departments and their data are separate. It is far too easy to abuse gathering and joining data on people otherwise. History did teach us these lessons, and it's continuously visible as well today, fortunately at small scales just because they are separate.
It would truly be a nightmare scenario to have all government databases under a single potentially corrupt roof or having someone with access to all of them cough.