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.