Donald Trump’s presidency might be a catastrophe of epic proportions, but you have to grant him one thing: He’s made Americans pay attention to whatever the commander-in-chief is saying. On April 28, for instance, the White House issued the kind of presidential proclamation that is usually the proverbial tree falling in the forest, unheard and unseen. Like every president since Eisenhower, Trump proclaimed May 1 to be Loyalty Day—the occasion first invented during the Red Scare of the 1920s to counter the traditional pro-worker May Day. JFK had done it, LBJ had done it, Obama had done it. But when Trump did it, half the country—and all the Twittersphere—went into panic mode. What was this new Loyalty Day that Trump had come up with? Another step on the road to fascism?

For once, there was actually nothing to panic about. But the reaction spoke volumes. Loyalty Day seemed to symbolize the defining neurosis of Trump’s presidency: his maniacal need for loyalty above all else. It’s the reason he has failed to nominate anyone to fill hundreds of key federal jobs. It’s the reason he has surrounded himself not with “the best” advisers, as he promised in the campaign, but with a gaggle of ego-stroking family members, hangers-on, profiteers, and rogue ideologues. And it’s why, the week after Loyalty Day, “loyalty” became the pretext for his decision to fire the FBI director who was investigating Trump’s own campaign. James Comey’s dismissal left little doubt that Trump’s preoccupation with personal loyalty—even more than incompetence, stupidity, or corruption—could be the thing that wrecks his presidency.

Loyalty Day seemed to symbolize the defining neurosis of Trump’s presidency: his maniacal need for loyalty above all else.

As Comey told associates at the time, and testified last week in Congress, the trouble began when he refused Trump’s demand that he pledge his personal fealty, as if he were a monarchal subject. Instead, Comey promised to be “honest”—and thus loyal to the duties of his office, rather than the whims of his boss. After the firing, Trump denied that he’d asked Comey for loyalty, but emphasized that it wouldn’t have been wrong if he had. “I don’t think it would be a bad question to ask,” he told his friends over at Fox News. “I think loyalty to the country, loyalty to the United States, is important. You know, I mean, it depends on how you define loyalty.”

We know how Trump defines it—and that’s the problem. This is a man who, at a campaign rally, asked his supporters to pledge allegiance not to the flag, but to him. This is a man who made his bodyguard the head of Oval Office Operations, a key gatekeeper role. Every president needs a few die-hard loyalists around him; Trump needs everyone to be a die-hard loyalist. And since Trump already rivals Richard Nixon as the most dangerously isolated president in American history, it’s essential to understand why.

In some ways, the tunnel-vision insistence on loyalty is the least surprising thing about Trump’s presidency. After all, the man has always been a self-described “loyalty freak.” Asked a couple of years back what he looked for most in an employee, he shot back the “l”-word without pause. Some observers have chalked this up to Trump’s paranoid personality and deep-seated insecurity. More tangibly, it stems from his business past: Navigating the notoriously cutthroat, mob-ridden, and litigious world of New York real estate, he naturally came to value personal allegiance above all else. When your business model orbits entirely around yourself, everyone else must yield to your gravity.