The problem was that Trump hired Bolton for his style but got his substance. Trump wants to negotiate with North Korea; Bolton did not. (In June, Bolton seemed to indulge in a historical pun by exiling himself to Mongolia while Trump met with Kim Jong Un.) Bolton favors regime change in Iran, by military means if necessary; Trump also detests the government in Tehran but resists armed conflict. From hot spot to hot spot around the globe, Trump and Bolton simply saw things differently, making conflict between them inevitable. Trump also reportedly disliked Bolton’s trademark mustache.

Yet focusing on the specific conflicts between Bolton and Trump misses the point. The problem is not that Trump doesn’t get along with his national security adviser; it’s that he doesn’t want one in the first place. The point of the job is to advise the president on national-security matters and to coordinate the efforts of the sprawling national-security bureaucracy to ensure the government works smoothly. But Trump doesn’t want advice, and he prefers to keep his subordinates in conflict.

Bolton was the third person to hold the job, each with a very different style and résumé, and each appointment has ended acrimoniously. The first, retired Lieutenant General Michael Flynn, was a career military officer, yet also essentially an insurgent who wanted to tear down much of the existing system. Just how much became clear less than a month into the administration, when he was fired after The Washington Post revealed that Flynn had lied to Vice President Mike Pence about conversations with Russian officials. As it turned out, Flynn had also lied to FBI agents, a crime to which he later pleaded guilty. (Coincidentally, there was a court hearing in Flynn’s case this morning as Bolton was being fired.)

To replace Flynn, Trump hired Lieutenant General H. R. McMaster. Like Flynn, he was a career military man, but the similarities ended there. McMaster was meticulous, careful, and devoted to order, both internally, in terms of policy process, and externally, in his commitment to alliances. Trump clashed with him on both process and policy, culminating in the abrupt termination of his White House service and military career.

Then came Bolton. If Flynn was an antiestablishment bomb thrower, Bolton was an ur-establishment bomb launcher, a veteran official who loves conflict, whether intramural or international. Unlike McMaster and Flynn, he had mastered the ways of the executive branch, which may help explain why he lasted as long as he did. But Bolton approaches government as a tool to achieve his long-standing goals, which brought tension with Trump, and with Secretary of State Mike Pompeo, who has more loyalty to the president and less of a fixed ideology.

By the end of his term, Bolton seemed to be on the outside both literally and metaphorically. Bolton had to beam in from Warsaw, where he was traveling, for a discussion in late August about inviting Taliban leaders to Camp David for peace negotiations. “Mr. Bolton was the leading voice against the deal on the inside as Mr. Pompeo’s allies increasingly tried to isolate the national security adviser,” The New York Times reported. It seems both sides got their way: Bolton lost his job, but Trump also pulled the plug on the conference.