What is surprising about the four-page letter that was issued by Attorney General William Barr on Sunday afternoon is what it lacks. The summary of the principal findings of Robert Mueller’s investigation contains no reference to President Trump’s businesses. That suggests that Mueller kept the focus of his inquiry quite narrow, and, apparently, did not investigate the President’s business dealings with oligarchs from the former Soviet Union who have ties to Vladimir Putin. We will not know the full extent of the special counsel’s work until his report is released or he testifies before Congress. If Mueller did not examine Trump’s businesses, then the American people are poorly served.

It remains astonishing that, even after the conclusion of Mueller’s investigation, we know so little about which individuals or corporations from around the world—and particularly from Russia and the rest of the former Soviet Union—have invested in Trump’s business endeavors, or given him money, and what he has promised them in return. The President, his family, and his company have gone to great lengths to hide this information from us. It is not unreasonable to ask if there are wealthy and powerful oligarchs who have compromising information about the President that they could use to sway him and alter his policies. Mueller had a narrow remit, and it seems he took that narrowness to heart. But there is no way to understand our President’s relationship with the world, his motivations and vulnerabilities, without a far richer picture of his central area of concern—his business—over the past decade.

The key period begins in 2010, when Trump and his businesses were suffering a series of many watershed crises. All major banks except for Deutsche Bank refused to lend him money, his television program was sinking in the ratings, his casino business was in the midst of a humiliating collapse, and the lifeblood of his company—the steady transfer of cash from his father and then his father’s estate—had run out. Yet, that same year, Trump began an unprecedented spending spree, pouring hundreds of millions of dollars into several money-losing golf courses, particularly Doral, in Florida, and two courses in Scotland. At this moment, the Trump Organization is seeking approval to spend nearly two hundred million dollars to develop housing and amenities for his course in Aberdeen.

This sudden windfall has never been clearly explained. Eric Trump once told a reporter that the funding came from wealthy Russians who love golf. He subsequently denied ever saying this, and instead claimed that it came from “incredible cash flow.” This is confusing. The Trump Organization is best understood as a series of unconnected high-risk bets and schemes, most of which have lost money. Much of its cash flow came primarily from the legacy properties in Queens and Brooklyn developed by Trump’s father, Fred, and four office towers that Trump, quite accidentally, found himself co-owning. There is nothing that Trump was doing in 2010 or the years afterward that suggests a sudden increase in his “incredible cash flow.” So where did the money come from? Barr’s summary does not address this vital question.

It is no small matter for the President of the United States to have had a dramatic and unexplained increase in cash during the financial crisis and in the years leading up to and including his Presidency. As I have written in the past, it is notable that Trump began spending this money at the same time that he befriended several oligarchs in the former Soviet Union, notably the Mammadov family, of Azerbaijan, and the Agalarovs, originally from Azerbaijan but now based in Moscow. Both families are likely money launderers with a penchant for spending fortunes on money-losing golf courses. We know that Trump was paid millions by both families for a failed 2012 luxury apartment building and for the 2013 Miss Universe pageant in Moscow—and that he and his children stayed in close contact with them for years afterward.

There was a hope—perhaps held in vain—that Mueller would recognize that it would not be possible to draw conclusions about the President’s relationship with Russia without understanding how Trump made so much money in recent years—and, most important, how much, if any, of that business came from oligarchs from the Soviet Union. The investigation into the President’s businesses will now be the work of Congress and of local, state, and federal prosecutors. The President will accuse them of being sore losers, of ignoring the seeming vindication described in Mueller’s report. They will be told that they are politicizing the Presidency. But a simple fact remains: we have no idea who gave our President hundreds of millions of dollars and what he might owe in return. We have a right to know.