What shines through the testimony of Marie Yovanovitch is her disorientation. She is a veteran diplomat at the peak of her career, and in one of the most challenging but important posts in US foreign policy. But she had no clue what was happening inside her own government.

On 24 April this year, she received a call from Carol Perez, the director general of the foreign service, speaking to her in cryptic tones as if Yovanovitch’s life was in danger if she remained at her ambassadorial post in Kyiv. She spoke as if there was a threat too awful to describe clearly on a phone line.

“She said that there was a lot of concern for me, that I needed to be on the next plane home to Washington,” Yovanovitch recalled in her testimony to the congressional committees conducting impeachment hearings. Taken aback, the ambassador to Ukraine wanted to know what the sudden panic was about. Perez just told her: “I don’t know, but this is about your security. You need to come home immediately.”

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Confused and anxious, Yovanovitch flew to Washington to find a state department she no longer recognised.

A few months earlier, her superiors had been so pleased with her work in Kyiv - demonstrating support to the Ukrainian government while holding it to account for its pervasive corruption – that they pleaded with her to extend her posting by an extra year. Now, on her return to Washington, she was being asked to leave without even the dignity of hosting the annual Fourth of July reception.

The top officials were apologetic but shifty. Phil Reeker, the acting assistant secretary of state for Europe and Eurasia told Yovanovitch that Donald Trump had wanted her out of the post since the previous summer. It was the first Yovanovitch had heard about it. Why in that case had the state department tried, as recently as March, to cajole her into staying on? It did not make sense and nothing was being clearly explained. Kafka had come to Foggy Bottom.

When Yovanovitch went to see the deputy secretary of state, John Sullivan, he confirmed that she had lost the confidence of the president, again without explaining how or why. His explanation of the urgent call in the middle of the night was equally bizarre.

“They were worried that if I wasn’t physically out of Ukraine, that there would be, some sort of public either tweet or something else from the White House,” Yovanovitch testified. “And so this was to make sure that I would be treated with as much respect as possible.”

The ambassador had been evacuated not because of some outside threat, but in fear of a tweet from the president. The terrible capricious power of Trump’s Twitter outbursts, and their paralysing effect on the administration, is a striking theme of the Yovanovitch transcript.

She had grown accustomed to a whispering campaign against her from Ukrainian politicians and businessmen for whom she had made life difficult, but when an article appeared on The Hill news site, recycling Ukrainian smears against her, she asked for a show of support from her secretary of state, Mike Pompeo. Such support for an ambassador in a critical post should have been a given, but Pompeo remained silent.

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“What I was told is that there was concern that the rug would be pulled out from underneath the state department if they put out something publicly,” Yovanovitch said. “You know, that perhaps there would be a tweet of disagreement or something else” from the president.

The best Pompeo did for his ambassador in Ukraine, according to her testimony, was to contact Fox television’s Sean Hannity, to ask if there was any truth to the smears against Yovanovitch, which Hannity was helping to push. That a secretary of state had to go to a talk show host to find out what was going on in Ukraine neatly encapsulates the nature of the Trump presidency.

In less than a year, Yovanovitch’s world had been turned upside down. The state department to which she had devoted her career had been, in her eyes at least, a grand ocean liner of diplomacy. Once its course was charted, everyone knew their role in getting to the objective. Other nations could only look on in awe.

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Now, in Ukraine and elsewhere, a shadow foreign policy has emerged, whose true goals are known to the president, his family and his personal lawyer, Rudy Giuliani. Through that channel, a discredited Ukrainian prosecutor and two obscure Florida businessmen who had become Giuliani’s sidekicks, wielded more influence than the entire state department. They fought to get Yovanovitch removed and they succeeded.

For experienced diplomatic veterans like Yovanovitch, this kind of corruption and dysfunction was all too familiar. They see it every day in the world’s autocracies.

“This is the sort of stuff we report on, how the president’s family and its hangers-on run everything. Now foreign diplomats are saying the same things about us,” one US foreign service officer observed recently.

In the space of a few weeks in spring, Yovanovitch went from sending cables back to Washington about her embassy’s uphill struggle in containing to Ukraine’s endemic corruption, to being warned by a concerned Ukrainian minister and oligarch, Arsen Avakov, to watch her back. Things were so bad, Ukraine was afraid of getting enmeshed in Washington’s venality.

In her testimony to congress, Yovanovitch grew emotional and asked to be excused, when expressing her “dismay and disappointment” about her fate and the fate of US foreign policy. Her disillusion is widely shared among American diplomats, who once felt themselves part of a mighty, venerable institution, and are now all too aware of its fragility.