The Washington Post, New Yorker and New York Times all searched for answers, gawking at the hundreds of millions Trump spent on golf properties without uncovering the source of the funds. The resort investments particularly mystified Trump skeptics, who wondered why he would risk more than $175 million of his own cash on money-losing assets. Politicians in Scotland, home to two Trump golf resorts, called for something known as an Unexplained Wealth Order, intended to expose illicit money, especially in the hands of politicians. Meanwhile, Forbes conducted its own investigation and, after combing through stacks of documents, believes it solved the mystery.

Much of the financing—roughly $250 million—came from members of Trump’s private clubs, who paid initiation deposits that they could theoretically get back if they tired of the place after 30 years. Unlike bank loans, these deposits came with no interest payments and no mortgage filings, keeping the liabilities both cheap and hidden. More money—over $450 million—landed via a series of windfalls, including loan repayments, tax refunds and property refinancings, that attracted little attention but provided tons of cash.

Trump, who failed to get additional financing from his go-to lender, Deutsche Bank, emptied his pockets, deploying almost all of his stockpile as he simultaneously remade the European golf resorts and bankrolled a presidential campaign. 

Although his member-financing now looks brilliant, his cash-bet seems reckless, depleting Trump’s liquidity to such an extent that, after the 2016 election, he apparently had to secure an emergency loan, which he also kept under wraps. Trump survived, though, and today his golf-and-club portfolio is the fastest-growing part of his real-estate empire, worth an estimated $1 billion.