“Nothing like this has ever happened before in the history of Saudi Arabia, giving the sense the kingdom is entering into unchartered waters with unknown consequences,” David Ottaway, a Middle East fellow at the Wilson Center, said in a statement. He added that the actions “could well threaten the House of Saud’s stability for years to come.”

More than half of Saudi Arabia’s population is under the age of 25—and the kingdom’s youth is where the crown prince draws much of his support. Saudi Arabia’s old guard, whose hold on the reins of power is slipping quickly, is much more skeptical of the pace of change under Prince Mohammed bin Salman. While much of the recent attention has focused on Saudi women gaining the right to drive, the crown prince’s other initiatives are the ones that have caused worry within the kingdom. The conflict in Yemen is not only seen as a proxy war against Iran, Saudi Arabia’s main regional rival, it is also seen largely as one that cannot be won. Add to this the Saudi-led blockade of Qatar, and the crown prince’s Vision 2030 program, which aims to reduce the kingdom’s economic dependence on oil, as well as his plan to sell 5 percent of Saudi Aramco, the state-run oil company. The crown prince says he believes the sale will yield $100 billion.

President Trump spoke to King Salman, and a readout of the call provided by the White House did not discuss the Saudi arrests. It said the two leaders discussed the situation in Yemen, where Saudi-led forces are involved in a proxy war against Iran-backed rebels. Trump reportedly also thanked the king for spending $15 billion to buy the THAAD antiballistic missile defense system. Earlier, the U.S. president tweeted that he hoped Aramco would be listed on the New York Stock Exchange.

But if economic reform is a cornerstone of the crown prince’s plan, then the arrest of Prince Alwaleed, one of the richest men in the world, is a funny way of showing it. The billionaire investor has large stakes in the tech giants Apple, Twitter, and Lyft, as well as traditional investment targets such as Citigroup and News Corp. He is estimated to be worth $17 billion, according to Forbes, and is a frequent interlocutor of Western leaders and companies. News of his detention prompted a nearly 10 percent slide in Kingdom Holding, his investment firm. Ottaway, the Middle East expert, pointed out that the arrest of Prince Alwaleed “could well dampen international interest in investing in the crown prince’s much-heralded Vision 2030 to make the non-oil private sector the new motor of the economy.”

That may well be true, but the crown prince is perhaps betting on the long game. With the Trump administration firmly in the corner of the ruling royal family and the last vestiges of opposition swept away, if all goes according to his plan, Prince Mohammed bin Salman will remake his country in his image. But as he awaits his ascension to the throne, amid the turmoil he has created, he may also find that uneasy lies the head that wears a crown.

* This article originally misstated the date of Prince Mohammed's ascension. We regret the error.