Three-time Olympian Vaultier, 26, and 2010 Junior World Champion Olyunin, 22, both won each of their rounds leading up to the final and did not face one another until the final round.
After the finish, Vaultier, who was racing with a torn ACL which he had suffered in bad crash during the Lake Louise World Cup event last December, pumped his arms in the air and screamed wildly in jubilation.
"When I passed the finish line, I think I was still up in the air [from the last jump]", said the Frenchman. "My luck was that I didn't compete against the Russian until the finals. I think that played in my favour".
His rival from Siberia had said a year ago that he had planned to retire after Sochi 2014. But he showed now signs of being done during his races, which thrilled a partisan crowd.
Wearing Russian colours and waving flags and banners, the spectators shrugged off the constant rain and fog and helped cheer Olyunin down the course, roaring loudly with each of his wins.
"I think he's a great rider and he deserves this”, he said about the new Olympic Champion, before joking: "But I will never forgive him for it".
The men's snowboard cross event was originally scheduled for Monday, but heavy fog caused officials to postpone it. Visibility had improved at the beginning of Tuesday's racing but as the morning progressed the fog started to cover the course and it became harder to see, although enough visibility remained to run the finals.
"I enjoy the adverse conditions. I've never minded bad weather - it's just something you have to prepare yourself for", Deibold said.
The 27-year-old did not make the USA snowboarding team for Vancouver 2010 but went anyway as a wax technician to help his teammates. He said that gave him motivation to work hard to medal at Sochi 2014.