Mick Mulvaney, who left Congress for an array of Trump administration positions including director of the Office of Management and Budget (OMB) and acting White House chief of staff, is done.

"I called [Secretary of State] Mike Pompeo last night and let him know I'd be resigning from [his current role as special envoy to Northern Ireland]," Mulvaney said in an interview the morning after Trump supporters stormed the Capitol. "I just — I can't do it — I can't stay ... I can't stay here — not after yesterday. You can't look at that, yesterday, and think, 'I want to be a part of that in any way, shape, or form."

Indeed, you can't. But the fact still remains: Mulvaney was. He was part of it in many ways, shapes, and forms, and yet he seems sincerely shaken here. He rubs his head in shock. Maybe he's acting, or maybe I'm naive, but he looks to me genuinely bewildered. And yet: How could he not know?

How could any of them not know? Mulvaney said he expected other White House staff would similarly resign this week. The Washington Post reports the same. "A deep, simmering unease coursed through the administration over the president's refusal to accept his election loss and his role in inciting a mob to storm the Capitol," said a Post story early Thursday. "A trio of senior White House aides — national security adviser Robert C. O'Brien, deputy national security adviser Matthew Pottinger, and deputy chief of staff Chris Liddell — were contemplating resigning, according to three senior administration officials." Transportation Secretary Elaine Chao — Senate Majority Leader Mitch McConnell's wife — is reportedly resigning. Two of first lady Melania Trump's aides have already bounced, as has the deputy White House press secretary. Some staffers "were mortified," the Post article said, at Trump's belated directive for rioters to go home, which he paired with continued insistence that the election was stolen, the very lie that sparked the riot.

This is the mystery: Mortification suggests upset expectations. It is mortifying if, as an adult, you are incontinent in public. It is not mortifying if a toddler poops his pants, because we expect that from toddlers. Likewise, there are many terms of moral condemnation that may be aptly applied to what happened in Washington on Wednesday. We might be appalled, horrified, frightened, and so on. We might also be surprised events took this turn — I'm surprised myself, not because I thought better of President Trump or those under his thrall, but because I thought they'd continue to play-act their emotive extremism online, that the LARP would largely amount to legal theatrics, street scuffles, and Twitter beefs.

Mortification only makes sense if you thought Trump and his supporters had principles to preclude this. It relies on an assumption that Trump is not totally lacking in respect for truth, peace, rule of law — anything, really, beyond his own wealth, power, comfort, and ego. Mulvaney's apparent shock is only intelligible if he didn't understand anything about the man he worked with for four years. And how could he not understand? How could he not know?

Mulvaney was first elected to Congress in 2010, the peak Tea Party year. He was a founding member of the House Freedom Caucus and palled around with people like former Rep. Justin Amash, who would later leave the Republican Party for reasons including its embrace of Trump, whose impeachment he supported. Mulvaney went dead in the other direction.

Perhaps he thought he could do some good. Perhaps leading the OMB seemed like an opportunity to slash the regulatory state in a way he could not achieve as a congressional backbencher. Perhaps taking on the duties of chief of staff seemed like an opportunity to restrain Trump's worst impulses. Perhaps Mulvaney somehow thought he'd succeed where Reince Priebus and John Kelly failed. Perhaps all these hopes overwhelmed his ability to observe reality.

Perhaps it was the intoxicating proximity to power. Perhaps he grew numb, each rationalization reinforced by a right-wing commentariat in which too many claim, as Fox News host Tucker Carlson did Wednesday night in his recap of the day's chaos, that everything bad is the other side's fault. Perhaps it was an ironclad compartmentalization, an inner mantra that the crazy is worth the policy wins, the tweets a fair trade for the tax cuts, the deception the price of deregulation, the ethical putrescence the cost of putting conservatives on the Supreme Court.

Perhaps he simply did not want to know.

Yet he should have known. Mulvaney and other Trump administration members should not be mystified. They may have reasons, but they are without excuse. Trump lies about many things, but he doesn't hide his own character. Nor do his diehard supporters — the three in 10 Republicans who say they "strongly support" the storming of the Capitol — conceal their acceptance of that character. They like it, and they've openly said so for five years.

Trump's not mortified, and they're not mortified, and White House staff shouldn't be mortified either. They should be repentant.