In Volume 2 of "Political Order & Political Decay," Frances Fukuyama describes the balance between the elected bodies and the civil service. If the elected bodies are micromanaging the bureaucracy, the bureaucracy will obey the elected bodies "to the letter of the law," being totally inflexible to change as the needs of the citizenry changes (at least until the legislation changes). If the bureaucracy develops its own mind, then the legislation and the elections won't matter as to how the country is run. There is a balance between these two extremes.
My anecdotal political experience is that elected politicians really shouldn't change the bureaucracy overnight. It can bite back. In my TDG book, I have identified the bureaucracy as one of several adversaries of the politicians.
I suspect that political science circles have discussed the relationship between the elected bodies and the bureaucracy. I have not encountered much. Certainly the political writers on Medium are not going in this direction. This relationship is not "eyeball-catching" enough for political writing and reporting. Yet it is so important.
As for the Democrats taking control of the American civil service, I'm not seeing it. But I am also too far away to make an accurate determination.
I believe the TDG will find a better balance between the elected bodies and bureaucracy. They will be better able to make the changes as society changes.