Vaast on Monday became the first Olympic champion from the French Pacific island.
"The mana was with me from the start, every day I felt it," the 22-year-old told AFP, referring to a supernatural force that, according to Polynesian beliefs, permeates the universe.
"I couldn't see it but I felt it, and 'voila', I did it -- an Olympic champion," he said.
Vaast beat Australian Jack Robinson after taking the two best waves of a high-level match.
The entire island rooted for him.
"As soon as the first two waves were caught, we were all there blowing for there to be no more, and it worked," joked Polynesian President Moetai Brotherson.
Tahiti, with the Teahupo'o waves that often reach two to three metres and sometimes a lot higher, hosted a spectacular surfing competition, which was extended until Monday due to unfavourable winds last week.
Vaast's mother, Natou Thupalua, opted for some garden therapy to calm her nerves.
"When he competes in Tahiti, I garden," she said. "I planted anthuriums."
The newly crowned Olympic champion said he might need to do a bit of work in the garden now, too.
"When I get home, I'm going to have to use the rake because she cut everything," he smiled.
Thousands of Polynesians cheered their champion and Johanne Defay from the French island of Reunion, who won bronze in the women's final.
Three-time world champion Gabriel Medina of Brazil, who went into the Games as a widely tipped favourite, took the men's bronze.
- 'Something great' -
Last week an AFP picture of Medina kicking out of a wave went viral, becoming a defining image of the sport and the Paris Games.
Surfing was introduced as an Olympic sport at the Covid-delayed Tokyo 2020 Games and the success of the competition in Tahiti will help to further establish it on the programme.
"This could be the start of something great for French surfing," said French team coach Jeremy Flores, who competed in Tokyo.
With an American, a Brazilian, an Australian and a French surfer, the four best surfing nations were represented in the finals.
Tahiti, nearly 16,000 kilometres (9,950 miles) from Paris, was selected to host the second Olympic surfing competition in history with the aim of including France's overseas territories in the Games.
French Polynesia comprises more than 100 islands, including Tahiti.
It is one of several French overseas territories that span the Caribbean and the Pacific.
And the surfing competition could prove a long-term bonus for Tahiti.
The Olympic surfing event generated spectacular images and "an extraordinary promotional operation" for local tourism, said President Brotherson.
