The fact that Trump’s State Department is in shambles is not, at this point, debatable.

Recent data from the American Foreign Service Association (AFSA), the professional organization for America’s diplomatic corps, found that 60 percent of State’s highest-ranking career officers quit during Trump’s first year; the number of applications to join the foreign service dropped by half. Fewer than half of all top-level positions, political appointees nominated by the president and confirmed by the Senate, have been filled.

The question that remains is who’s to blame. A new article by journalist Ronan Farrow, published in the New Yorker on Thursday morning, sheds light on the question. The piece is deeply reported, featuring a wide-ranging interview with Tillerson conducted while he was in office. Farrow paints a damning picture of a dysfunctional State Department, brought to the brink of ruin by Trump and Tillerson in equal parts.

Trump’s management style emerges in the piece as a clear reason for State’s decline. The president’s top advisers are constantly at war with one another, struggling over influence in a pale imitation of Game of Thrones.

In the months prior to Tillerson’s ouster, there were constant rumors that he was on the verge of being ousted. Jared Kushner, who had been put in charge of Israel-Palestine negotiations, was allegedly the one spreading those rumors in a bid to expand his own influence over foreign policy.

Farrow describes an intense moment during their interview in which Tillerson reveals the depth of his anger toward the person responsible for spreading those rumors about him:

Tillerson leaned in and, for a moment, I realized that it must be unpleasant to be fired by him. “I know who it is [behind the rumor]. I know who it is. And they know I know.” According to multiple individuals who had heard Tillerson speak of the matter behind closed doors, this was a reference to Trump’s son-in-law and adviser, Jared Kushner. Before Tillerson’s departure, tensions between the two men had been flaring regularly, often in the form of a public-relations proxy war.

The fact that there was this level of hostility and tension between Kushner and Tillerson helps explain in why Tillerson — and by extension the State Department — struggled to be a prominent player in top-level foreign policy decisions.

A second problem is the White House’s utter disinterest in — or perhaps even disdain for — the work that State Department diplomats and even lower-level officials do in running the day-to-day management of US foreign policy.

The president, according to Tillerson, put little effort into filling vacant jobs at the State Department, including vital posts like ambassadors to Egypt, Saudi Arabia, and South Korea. Tillerson complained to Farrow that he would propose names and never hear back from the White House about whether they could be formally nominated:

“They’ve not been easy,” [Tillerson] recalled, of his year of conversations with the Trump Administration about filling the open jobs. “The process over there has not been the most efficient, and they’ve changed personnel trying to improve it, I mean, many, many times. . . . It was very slow, it was very cumbersome, it was frustrating, at times, because you couldn’t get a sense of ‘What’s the issue?’ Someone seems to be kind of sitting in idle over there,” he said, sighing. “I would tell ’em, ‘Just give me a no. At least with a no, I’ll go get another name.’”

If the president doesn’t care about getting high-level appointees like ambassadors through Congress and into their jobs, then the State Department won’t function.

The third, and perhaps most important, reason for State’s collapse is that Secretary Tillerson was simply not well suited for his job. Before becoming secretary of state, Tillerson had spent years sitting at the very top of a massive multinational corporation, Exxon-Mobil. Tillerson was top dog — his office was even referred to as the “God Pod” by Exxon-Mobil employees. He was a powerful Texas oil executive who probably didn’t have his word questioned very often.

But when he became secretary of state, he suddenly had to defer to the whims of the president — a man he reportedly once described in a meeting with staffers as “a fucking moron” and who also likes to see himself as the toughest guy in the room. As Farrow explains, that dynamic didn’t exactly go so well:

“The only person that I have to worry about is the President of the United States,” Tillerson told me. But that relationship was, likewise, fraught. Tillerson’s Texas swagger, the source close to the White House said, irked Trump. “You just can’t be an arrogant alpha male all the time with Trump. You have to do what [Secretary of Defense Jim] Mattis does, which is, ‘Mr. President, you’re the President, you’re smarter than me, you won, your instincts are always right, but let me just give you the other view, sir.’ Then you have this guy coming in,” the source said, referring to Tillerson, “going ‘Well, I guess because I worked for so many years in the oil business, I have something to say. You don’t know much about the region, so let me start with that.’ I mean, honestly, condescending.”

CIA Director Mike Pompeo, Trump’s pick to replace Tillerson as secretary of state, reportedly has a much better relationship with the president. If he’s confirmed, he’ll have to keep it that way — or else the deep damage done to America’s diplomatic corps during the Tillerson era won’t be healed.