The owners of major American sports franchises generally do not dive headlong into geopolitical firestorms.

But not many owners have the background of Joe Tsai, a Taiwanese-born billionaire who recently became the primary owner of the Brooklyn Nets. This weekend, Tsai surprised many when he weighed in after the N.B.A. responded to a Twitter post by a league executive supporting Hong Kong’s anti-government protesters, just as a furor over the tweet reached a fever pitch.

Tsai replied on Sunday night — roughly 48 hours after Daryl Morey, the general manager of the Houston Rockets, had tweeted, “Fight for freedom, stand with Hong Kong,” a comment that sent a shudder through N.B.A. headquarters, as well as the league’s partners at the highest echelons of Chinese basketball.

Morey’s boss, the Rockets owner Tilman Fertitta, rebuked him on Twitter, and Morey deleted the post. The N.B.A. issued a statement saying that it was “regrettable” that Morey’s tweet had offended people, but that “the values of the league support individuals’ educating themselves and sharing their views on matters important to them.”

Then, as denunciations of the N.B.A. rolled in from the Chinese mainland, American politicians from both parties rallied behind Morey, condemning the league for not standing more firmly behind the executive.

Tsai — known in China as the man behind Jack Ma, the founder of the Chinese e-commerce giant Alibaba Group — posted a lengthy open letter on Facebook, referring to the pro-democracy protesters in Hong Kong as a “separatist movement,” an echo of language from Beijing.

Tsai also criticized Morey, calling his Twitter post “damaging to the relationship with our fans in China.”

For months, Tsai has not been outspoken as protests against the central government in Beijing roiled Hong Kong. Demonstrators have accused the ruling Communist Party of trying to curtail civil liberties in the semiautonomous territory. “Fight for Freedom” and “Stand with Hong Kong” are often chanted at the protests.

As a team owner, Tsai, who declined to comment for this article, has emphasized helping the N.B.A. make inroads in China, where basketball has become the most popular sport. While the letter may have helped his efforts, it also crystallized the league’s decision to bow to economic pressure from its partners in China over support in the United States for Morey and the Hong Kong protesters.

Before this weekend, Tsai, 55, was not known as a political figure. Only as a businessman.

In China’s tech industry, Ma is considered the creative force, and Tsai the one who turned ideas into action. Ahead of Alibaba’s initial public offering in New York in 2014, Tsai worked long hours with bankers and investors to help pull off the biggest-ever public offering.

The offering made Tsai one of the world’s wealthiest people. Forbes ranks him as the 147th richest person with a net worth of $9.5 billion. The son of a lawyer, Tsai came to the United States at the age of 13 to attend the Lawrenceville School, a private boarding school in New Jersey. He attended college at Yale and earned his law degree there, too.

While working at the Swedish investment company Investor AB in 1999, he went to check out an internet start-up called Alibaba in Hangzhou, in eastern China. Investor AB passed on the opportunity to invest, but Tsai decided to quit his job to join the start-up.

Ma, who worked out of his apartment with about 20 young associates, was surprised. Tsai was making around $700,000 a year, and Ma said he could afford to pay him only about $7,000. Tsai would help bring in key investors, such as Goldman Sachs and SoftBank, and pave the way for Alibaba to become a conglomerate that transformed how the Chinese shop.

Tsai was in charge of Alibaba’s overall investment and growth strategy until earlier this year. He still holds the title of executive vice chairman. He and Ma, who retired as executive chairman last month, are the only lifetime members of the Alibaba Partnership, a group of a few dozen employees with tremendous power over the company’s board and leadership, as well as its bonus pool.

Those who know Tsai describe him as smart and low key, someone who intentionally stayed in the shadow of the eloquent and high-profile Ma because he believed that a company needed only one spokesman.

In recent years, Tsai gradually drifted out of Ma’s shadow. He has appeared at tech conferences and given talks at Lawrenceville and Yale, but has rarely spoken about politics.

By Monday afternoon, Alibaba’s Taobao, a sales website, had essentially taken Houston Rockets products off the platform. The official Weibo account of the People’s Daily, the Communist Party’s official newspaper, quoted an Alibaba spokesman as saying that Morey’s Twitter speech had severely hurt the feelings of the Chinese people.

Tsai’s foray into professional American basketball was unusual. The vast majority of professional sports franchises in the United States are owned by white men, not people of color. Also, the acquisition was a rare example of an American sports team being acquired with mostly foreign money — although in this case, the franchise’s previous owner was a Russian billionaire. But Tsai seemed like an ideal fit for the N.B.A., especially to tap into the rabid basketball fan base in China.

In October 2017, Tsai paid a little more than $1 billion to acquire 49 percent of the Brooklyn Nets from Mikhail D. Prokhorov; the team had achieved mostly middling results on the court since he offered to buy the franchise in 2009. That deal came on the heels of several Chinese entrants into the sports market, such as a $650 million acquisition of the Ironman competition in 2015 by the Chinese conglomerate Dalian Wanda.

Tsai played lacrosse at Yale, and just months before the announcement of the Nets acquisition he purchased the San Diego franchise of the National Lacrosse League. At Yale Law School, Tsai occasionally played pickup basketball with a future Supreme Court justice, Brett M. Kavanaugh. Both of Tsai’s children also play basketball.

Earlier this year, Tsai purchased a W.N.B.A. team, the New York Liberty, from the Madison Square Garden ownership group. In April, the Liberty drafted Han Xu, a 6-foot-9 center, a Chinese national with enough of a following in her home country to draw comparisons to Yao Ming’s journey to the United States.

Tsai clearly saw the Nets as an opportunity to use basketball to bridge what he saw as a divide between China and the United States.

In May, before an exhibition game between the Liberty and the Chinese national team, Tsai told reporters: “I’m steeped in this discussion and find myself having to explain China to Americans a lot. This game, by bringing the national women’s team from China, is a platform for the two cultures to see how each other compete. You learn a little more about each other’s cultures. This is absolutely important. If there were more opportunities for me to support these kinds of changes, I’d do more of that.”

This summer, the N.B.A. announced that Tsai had acquired the entire stake of the Nets, valued at roughly $2.35 billion, a league record. The league — as well Tsai — has a great deal riding on his investment in the Nets. The team made several expensive free-agent acquisitions this off-season, including Kyrie Irving and Kevin Durant. The Nets’ brass hopes the team will draw more fans after having some of the worst attendance numbers in the league last season.

And if all goes well for the N.B.A., and this controversy eventually blows over, many of those eyeballs will come from outside the United States.

In the news release announcing the approval of the Nets sale, the N.B.A. commissioner, Adam Silver, said, “In addition to being a passionate basketball fan, Joe is one of China’s pre-eminent internet, media and e-commerce pioneers, and his expertise will be invaluable in the league’s efforts to grow the game in China and other global markets.”