I mean, there was technological and medical improvements, sure, and continued urbanization.
But that’s… those are some of our nations most shameful, inequal, racist years in its entire history. The federal government as it exists now was just getting started after we realized we needed it thanks to the civil war, and many local democratic systems were completely broken. More relevantly, we didn’t have cancer researchers, epidemiologists, the NSF, or, most relevantly, nuclear weapons.
Finally, a HUGE majority of the costs of the federal government are social security, Medicare, Medicaid, and defense spending. I doubt even the biggest libertarian on here could advocate cutting any those with a straight face, unless they’re young and don’t know anyone older than them, and/or advocates isolationism.
Regardless, this exact story makes it clear that the goal isn’t cutting the size of the government at all — it’s politicizing the civil service, and bringing it under the exclusive control of a supreme executive. They’re not exactly ashamed of it!