By the late 80s / early 90s, Trump and the Trump Organizaion were heavily in debt and could not find US lenders to back them. Trump has admitted as much, even going so far as to state it on The Apprentice in 2004.
“About 13 years ago, I was seriously in trouble. I was billions of dollars in debt.”
In the late '90s scouting began for a location and financing for a "Trump Tower Moscow" . Would Trump Tower Moscow become Trump's 'white whale'.
By 1998, two events came into play that would accelerate Trump's relationship with Russia. Donald Trump was looking for financing (Duetschbank) and the Russian stock market collapsed. The collapse of the Russian markets had the oligarchs looking for a safe haven to hide their money -- real estate and Trump's need for cash provided a happy marriage.
Trump needed the big spenders. He was renegotiating $1.8 billion in junk bonds for his Atlantic City resorts, and the tower was built on a mountain of debt owed to German banks. As Trump wrote in The Art of the Comeback, “It crushed my ego, my pride, to go hat in hand to the bankers.”
There has been a plethora written about Trump World Tower and Russian money (will open Google search results).
By 2002 the Trump Organization committed wholeheartedly to selling real estate to Russian oligarchs. In 2002 a presentation was made in Russia ...
The push to sell units in Trump World Tower to Russians expanded in 2002, when Sotheby’s International Realty teamed up with Kirsanova Realty, a Russian company. One reception at Moscow’s swank Hotel Baltschug Kempinski pitched the tower alongside Trump’s West Side condos and his building on Columbus Circle. (link)
By 2006, Trump was feeling flush again and on a global spending spree, buying up properties,
According to a later analysis by the Washington Post, “In the nine years before he ran for president, Donald Trump’s company spent more than $400 million in cash on new properties — including 14 transactions paid for in full, without borrowing from banks — during a buying binge that defied real estate industry practices and Trump’s own history as the self-described ‘King of Debt.’
Presidential ambitions were never far from the surface with Trump and the election of President Obama provided him with a burr, and the Burrther conspiracy was born. Trump used it to amass a twitter following of like minded conspiracy theorists that would prove invaluable in getting him elected in 2016.