Because the whole secret to the entire US Government is that it is run on the base assumption that nobody is really going to do anything bad. Everyone trusts that people are in their positions because they are good at what they do, and have good intentions.

The advantage of a bureaucracy is that it has more inertia than a glacier. They are not particularly prone to shock. This is literally the way the process works. Someone does something crazy, someone else issues an injunction, someone else calls an emergency session to debate it, meetings are had and laws are passed. Perhaps you're forgetting that Congress passed a fucking act over Terri Schiavo.

It'd be one thing if the whole apparatus were suddenly Trump-crazy. But Team Trump is pulling inward, not reaching outward. They've basically said "you're with us or you're with the terrorists" and then not waited for an answer.

Who, EXACTLY, walks up to the White House, armed, gets past Trump's personal security detail that are on HIS payroll, and puts the cuffs on the motherfucker and takes him to jail?

Is that a rhetorical question? Because it doesn't really matter. The discussion at hand right now is whether the DHS is bound by law to answer to the Executive, even in the face of district court rulings. We see defiance. I reckon they see "clarification." When it happens, Trump has either more power or less. If he ends up with "more", it becomes a congressional problem. If "less", it sets a precedent for future grabs.

Suppose Trump is impeached and refuses to go. Wouldn't be the first time a despot refuses to step down. That's very different from the point where the despot is no longer in charge.