A month before President Trump’s inauguration, Middle East envoy Steve Witkoff flew to the United Arab Emirates with two goals: discussing regional issues with the Abu Dhabi royal known as the “spy sheikh,” and attending a cryptocurrency conference. Less than five months later, Witkoff’s son, co-founder of the crypto venture World Liberty Financial, took the stage at a conference in Dubai to announce the company had struck a deal for the sheikh’s company to buy $2 billion of their new cryptocurrency. The expected tens of millions of dollars in annual profits would be split between the Witkoffs and their co-founders—and...