The U.S. Attorney in Manhattan closed the case against Yves Bouvier after the Da Vinci record, people familiar with the investigation say.

Federal prosecutors were looking into whether the Swiss art dealer inflated the sale price of artwork, but Bloomberg learned that the year-long investigation was fatally eroded when one piece sold to the Russian billionaire Dmitry Rybolovlev in an apparent swindle actually netted the potential victim a vast windfall. Rybolovlev had bought Leonardo da Vinci’s Salvator Mundi from Bouvier for $128 million only to read in the New York Times that it has actually just been sold for between $75 million to $80 million, with Bouvier netting the roughly $40 million difference. Still, when the piece went up for auction at Christie’s in November 2017, it sold for $450 million with fees.

The record-breaking haul was the “clincher” that ended the investigation, but the case against Bouvier in the U.S. had been falling apart even before the Da Vinci sale, sources told Bloomberg. Prosecutors feared it would be difficult to get a testimony from witnesses overseas. Another concern was finding a jury that would not be swayed by the fact that the alleged victim in the case is a billionaire Russian oligarch who had ties to Donald Trump. Rybolovlev bought a Palm Beach house from future President Trump for $95 million in 2008—$60 million more than what Trump paid, despite what was then a real estate market trashed by the recession.

Despite the end of the U.S. investigation, Rybolovlev and Bouvier remain locked in a bitter international legal dispute with cases pending in Monaco, Geneva, and Singapore. Rybolovlev has accused Bouvier of profiting $1 billion from him by selling him $2 billion in works at price points markedly higher than what Bouvier originally paid.