I think the conservative theory of the government is that a lot of it has accrued through inertia. And Musk in particular is a big believer in reversing the default assumption that you continue the status quo, and instead that you start by assuming that everything you're doing now probably should stop unless you can prove it's worthwhile.

Conservatives believe that government is subject to capture by benefitted constituencies, so that once something is in place it is very difficult to get rid of it. If even a relatively small number of people would be very upset by something go away, it's rarely worth it for anyone to make the thing go away. Even the benefit to getting rid of it is much, much higher than the cost of doing so, those who like the thing are concentrated and the ones who think it useless (or harmful) are diffuse. The political cost to getting rid of it is higher than keeping it. So it stays.

But if you get rid of it, it's never coming back, because then the equation is reversed. Now, putting it back requires political capital. You need someone to invest the resources to do that thing instead of something else - which gets a lot harder. If some program was created in the 1970's (for example), then it probably reflects the political passions and interests that existed at the time. But those passions and interests are different now. So while it could continue (because of inertia), it's not something that someone would create again today - which makes it less likely to get put back. It forces the government to more closely match the current political moment.

Right now, Trump has shown enormous savvy in attacking stuff that is among the less popular parts of government first. So a lot of the stuff he's killing may stay dead for good, even if Democrats win back the WH in four years.