That placed American hopes on Hamill’s teammate, Maggie Voisin. A veteran of the global freeski circuit, but still only 23, Voisin was making her third Olympic appearance. In 2014, at 15, she was at the Sochi Games but broke a leg in training before the competition. At the 2018 Games, she finished fourth. She arrived in China hungry for a medal but finished fifth.Most of the competition’s focus fell on Gu, the 18-year-old who was born and raised in California by a Chinese mother with deep roots in Beijing. She spent a couple of years with the U.S. national team before announcing, in 2019, that she would compete for China, in part to help build the country’s winter-sports market.Gu is an emerging star and a ubiquitous presence on Chinese television during these Olympics. Known as Gu Ailing, her face seems to be everywhere, including in the sky (a recent light show created a portrait of her using more than 500 drones) and in advertisements for her many Chinese sponsors. In the past year, she also has become a model for Tiffany & Company, Louis Vuitton and other high-end retailers.Her mother, Yan Gu, has a credential — most Americans could not bring family and friends to China because of pandemic-era restrictions — and has been at the events, cheering her daughter on.After landing a solid, pressure-packed qualification run in slopestyle on Monday, Gu confidently stood at the bottom of the course, awaiting a score that she knew would advance her to the final. She pulled from her pocket a shao bing, a type of Chinese flatbread, and bit into it. Within minutes, she and shao bing became a popular hashtag on Chinese social media.In the past month or so, and mostly in the past week since she won big air, the number of Gu’s Instagram followers — mostly in the West, rarely seen in China — has grown sixfold, to 1.1 million. She has far more followers on Weibo, a Chinese site akin to Twitter, where she posts more often. On Tuesday morning, her account was approaching five million followers, nearly five times as many as she had at the start of the year.