The crash on 20 December "was caused by human error by the pilot and the principal reason for the accident was flying at too low an altitude," public prosecutor Christophe Auger told the regional paper Sud Ouest on Saturday.
There were no technical or maintenance problems, the inquiry concluded.
The 46-year-old tea magnate was taking a helicopter tour of the 65-hectare Château de la Rivière estate in the Fronsac wine-producing region near Bordeaux the day after sealing the sale for 30 million euros.
His financial advisor and the château's former owner, James Grégoire, were killed along with him.
The flight took off late on a winter afternoon, when darkness had nearly fallen and visibility was limited, Auger noted.
The pilot had been drinking and alcohol consumption was "a contributing but not principal factor", he said.
Wealthy Chinese have developed a taste for prestigious French wines and several have bought estates in Bordeaux and Burgundy.