Unnamed sources who spoke to Bloomberg say special prosecutor Robert Mueller and his team of investigators are looking at Trump's business dealings.
Among other related matters, investigators are reportedly looking into the tens of millions of dollars anonymous Russian buyers have poured into Trump's properties.
FBI investigators and others are looking at Russian purchases of apartments in Trump buildings, Trump’s involvement in a controversial SoHo development with Russian associates, the 2013 Miss Universe pageant in Moscow and Trump’s sale of a Florida mansion to a Russian oligarch in 2008, the person said. [...]
Agents are also interested in dealings with the Bank of Cyprus, where Wilbur Ross served as vice chairman before he became commerce secretary. They are also examining the efforts of Jared Kushner, the President’s son-in-law and White House aide, to secure financing for some of his family’s real estate properties. The information was provided by someone familiar with the developing inquiry but not authorized to speak publicly.
Mueller is reportedly following a trail of breadcrumbs left behind by former U.S. Attorney for the Southern District of Manhattan Preet Bharara. Trump fired Bharara (along with every other U.S. attorney) while he was in the middle of a money laundering investigation, but the investigation continued under the acting attorney and the FBI had already gathered information from the probe.
Additionally, the New York Times reported last night that Deutsche Bank is finally expected to cooperate and hand over their records to Mueller. Trump owes millions of dollars in debt to Russian interests and the common assumption is that Deutsche Bank is their middle-man.
Mueller is following the money and that may ultimately be what this all comes down to; a sprawling RICO investigation with a side of treason.
From what we already know, it appears Trump would not be in the position he's in today if he wasn't bailed out by the Russians during his most recent bankruptcy. If that is the case, it should be obvious why Trump has never said a single bad word about Putin or Russia.