For weeks, Washington has been waiting to see how long National Security Adviser Michael Waltz could hold on. The answer, we now know, was 101 days.

Multiple outlets reported this morning that Waltz and his deputy, Alex Wong, would be leaving the Trump administration. His firing comes roughly seven weeks after he added The Atlantic’s editor in chief, Jeffrey Goldberg, to a Signal chat in which top administration officials discussed a strike on Yemen before and after it took place. In legal and security terms, the mortal sin was conducting official business in an unsecured and unpreserved forum; in political terms, it was including Goldberg. Trump acknowledged last week in an interview with Goldberg, and my colleagues Ashley Parker and Michael Scherer, that the scandal was “a very big story” and that his administration had learned “Maybe don’t use Signal, okay?” Trump reportedly hesitated to fire Waltz because he didn’t want to give the media a “scalp” or acknowledge that he cared, but his resolve apparently weakened.

Any other national security adviser would have been deservedly fired after the leak, but even without Signalgate, it’s hard to imagine that Waltz would have survived very long. (He did, at least, outlast the first national security adviser of Trump’s first term, Michael Flynn, who didn’t reach the one-month mark.) Waltz was one of the more respected and expert hands on Trump’s team, and that would have doomed him sooner or later.

Waltz’s demise was foretold shortly after Signalgate, when the 9/11–conspiracy theorist Laura Loomer, who holds no government role, persuaded Trump to fire several NSC staffers whom she believed were insufficiently loyal. Implicit in her critique and Trump’s acquiescence was a belief that Waltz wasn’t really on the team, either. Waltz is a right-winger and a convert to Trumpism, but he is not a blind loyalist. He won four Bronze Stars while serving in U.S. Special Forces. He worked at the Pentagon during the George W. Bush administration, and was elected to four terms in Congress. As national security adviser, he tried to bring his expertise to the service of the president.

The problem is that Waltz was trying to serve two masters. As I wrote in January, Trump doesn’t care about national security. He’s not against it, or actively trying to undermine it; he’s just not interested. He’s not interested in hearing reasoned advice, developed through a careful process, as the National Security Council has done—especially if this advice contradicts his impulses or ideology. On an issue like the strikes on Houthis in Yemen, where Trump has fewer interests to balance, problems don’t tend to arise. But on marquee issues that Trump can’t ignore, and where tough trade-offs and complicated strategy enter the picture—such as with Ukraine or China—someone has to start giving him news he doesn’t like.

Trump doesn’t want expertise. He started his presidency by sweeping out dozens of career officials whom his team viewed as Democrats in disguise or creatures of the establishment. Since then, the ground has continued to shift. My colleague Isaac Stanley-Becker reported recently that as Waltz’s control of the NSC slipped away, the real powers on the council were the longtime Trump adviser Stephen Miller and Trump’s Middle East envoy Steven Witkoff. These two represent very different models: the ideologue and the old pal, respectively. Miller treats the NSC “not as a forum to weigh policy options,” Stanley-Becker wrote, “but as a platform to advance his own hard-line immigration agenda.” The handy thing about ideology is that it effaces all the hard choices that a pragmatic approach to the world requires. Witkoff, meanwhile, seems to have neither an ideology nor any expertise that might interfere with his fidelity to Trump. Though he lacks diplomatic experience, he has been friends with Trump for years, and the president has sent him ricocheting around the globe—with little to show for it so far.

Trump’s allergy to expertise also helps explain why Defense Secretary Pete Hegseth appears to be on more solid footing than Waltz despite worse scandals: He, too, was involved in Signalgate. Though Hegseth was not the one who added Goldberg to the chat, Hegseth did share detailed attack plans in it. He also shared sensitive information with his wife and others who had no need for it, installed an insecure line into the Pentagon, and can’t manage to keep his staff from turning over. (“I think he’s gonna get it together,” Trump told my colleagues in an interview last week. “I had a talk with him, a positive talk, but I had a talk with him.”) Waltz’s ouster might be an ominous sign, however, for Secretary of State Marco Rubio, a traditional Republican and Trump critic turned vassal who holds another delicate foreign-policy job.

Now Waltz joins a list of discarded Trump national security advisers, alongside Flynn, H. R. McMaster, and John Bolton. That unhappy fraternity is only likely to grow. Every administration official serves at the pleasure of the president, and nothing incurs this president’s displeasure faster than trying to get him to care about national security.