None of this is surprising when you know the history:
1) Laundering dirty money has always been the primary function of New York City real estate.
2) Trump's grandfather needed to buy property to wash his take from Gold Rush brothels in Alaska, so that is how this all got started.
3) At a certain point the mafioso community in the Northeast went more or less legit, at least to the point where they could wash their own money through their frontline legal ventures.
4) That left a lot of dormant laundrymats like Trump Inc. looking for new clients. That is where the Russians come in.
5) The Russian mafia is not an independent organization like the Italians that New Yorkers were used to working with. Those old guys had government and police on the payroll, but in Russia the mafia is on the payroll of the state, an extension of the Kremlin in the post-Soviet reality.
6) This unprecedented occurrence of a major state becoming a de facto organized crime family is why many people believe Vladimir Putin is the wealthiest, and most powerful, person on earth.