On 11 October, nine days after the dissident Saudi journalist Jamal Khashoggi disappeared after visiting Saudi Arabia’s consulate in Istanbul, Donald Trump made a remarkable statement about his foreign policy priorities. At an impromptu press conference, the president was asked whether he would cancel arms sales to the kingdom if its leaders were implicated in Khashoggi’s likely murder. He responded that punishing Saudi leaders would cost the US money and jobs: “We don’t like it even a little bit. But whether or not we should stop $110bn from being spent in this country … That would not be acceptable to me.”

It was a clarifying moment for US foreign policy under Trump. For decades, successive US administrations pursued a similar path in the Middle East: security, military and diplomatic cooperation with repressive regimes like Saudi Arabia and Egypt, at the expense of promoting human rights and democracy. But several former presidents, including George W Bush and Barack Obama, obscured that reality with lofty rhetoric about respecting human rights. Trump dropped that pretense, and made clear that his primary interest would be America’s short-term economic and security concerns.

But by abandoning the veneer of US concern about political reforms and protecting dissidents, Trump also emboldened the region’s autocrats to become even more reckless and brutal. Since he took office in 2017, Trump signaled to Saudi Arabia’s leaders, especially King Salman and his son, the ambitious and ruthless 33-year-old crown prince, Mohammed bin Salman, that they can get away with anything – as long as they help keep global oil prices stable and continue buying US weapons.

With Trump’s green light, the young prince and his advisers intensified a series of destructive policies: Saudi Arabia continued a brutal war in Yemen that has killed tens of thousands of civilians; the kingdom imposed a blockade against its smaller neighbor, Qatar; the prince detained and forced Lebanon’s prime minister to resign; and he ordered the arrest of hundreds of Saudi activists and business leaders. Without any consequences for these actions, is it any surprise that Saudi Arabia expected to get away with the alleged abduction and murder of Khashoggi, who wrote columns for the Washington Post critical of the crown prince?

During the 2016 presidential campaign, Trump often criticized Saudi Arabia for its human rights abuses and supporting religious extremism. He even accused the kingdom of being behind the 9/11 terrorist attacks. (Fifteen of the 19 hijackers were Saudi nationals and members of al-Qaida, but the 9/11 commission report found no evidence that the Saudi government or its senior officials had funded the group.) Trump’s rhetoric changed as soon as he took office, partly because of a budding friendship between Bin Salman and Jared Kushner, the president’s son-in-law and senior adviser.

Saudi Arabia’s seduction of Trump reached a crescendo in May 2017, when he chose Riyadh as the first stop of his maiden foreign trip as president. Bin Salman and his inner circle realized that Trump craved respect and flattery, so they gave him an extravagant welcome. The streets of Riyadh were lined with billboards of the US president and Saudi king; Trump and his entourage were feted at multiple banquets with ostentatious displays of wealth and Salman presented Trump with the kingdom’s highest civilian honor, a large gold medallion. In the end, the Saudis persuaded Trump that he had earned greater deference than his predecessor, Obama.

Trump also used his trip to hype up a package of arms sales to Saudi Arabia that would total about $110bn over 10 years. But Trump has consistently inflated his administration’s role in selling US weapons to the kingdom; much of the military equipment that the Saudis planned to buy had already been approved by the Obama administration. And the Saudis have not closed any major new arms deal under Trump.

By the end of his visit, it was clear that Trump had aligned US foreign policy with Saudi Arabia’s vision of the Middle East, which portrayed its rival Iran as the greatest threat. And that unleashed Bin Salman to carry out even more destruction. In Yemen, Saudi Arabia and its allies, especially the United Arab Emirates, continued a brutal bombing campaign and naval and air blockade launched in March 2015 to dislodge Houthi rebels from the country’s most populous areas.

The Saudi-led war in Yemen triggered a humanitarian catastrophe, which by some estimates has killed nearly 50,000 people. More than 8 million Yemenis are on the brink of famine, and 1.1 million are infected with cholera. Several United Nations investigations found both the Houthis and the Saudi-led coalition responsible for war crimes, but the Saudis and their allies have caused far more civilian deaths with air strikes. And the US is probably culpable for these war crimes because it provides the Saudis and Emiratis with missiles and bombs, intelligence assistance in identifying targets and mid-air refueling for warplanes.

As the Yemen war drags on, more members of Congress are asking why the US is so deeply involved in this conflict. Last year, the Senate narrowly approved the Trump administration’s sale of over $500m in laser-guided bombs and missiles to the Saudi military. Since Khashoggi disappeared on 2 October, many in Congress – and in Washington’s foreign policy establishment – have turned against Saudi Arabia and especially its crown prince.

Even if Trump maintains his unwavering support and his cynical calculation that a single dissident’s life is not worth billions of dollars in weapons sales, Congress could still punish the Saudis for Khashoggi’s apparent death by rejecting future arms deals, and limiting US military involvement in the Yemen war. In the end, Bin Salman could pay more dearly for the life of one critical journalist than for all of Saudi Arabia’s other destructive actions.