Before finding a path to Silicon Valley, Mr. Rizvi invested in telecoms and manufacturing, but his biggest moves were in the entertainment industry. In 2004, he asked a mutual friend to introduce him to Jeff Berg, then chairman of International Creative Management, the talent agency, which was looking to expand. A year later, Mr. Rizvi led a private equity investment in I.C.M., taking a controlling stake for $100 million — with $95 million in debt financing from Merrill Lynch.

That created a platform for subsequent deals in Summit Entertainment, the production company that snagged the rights to the Twilight series, and a deal with Hugh Hefner to take Playboy private. Those deals piqued the interest of other private equity investors.

But it was not always smooth sailing. Mr. Rizvi and other executives at his company, Rizvi Traverse, are facing two lawsuits from disgruntled investors in Michigan and Texas, related to a film loan that went sour in 2008. And at I.C.M., management was so unhappy with their private equity overlord that they bought out Mr. Rizvi’s stake and that of Mr. Berg, who had brought Mr. Rizvi into the company in the first place.

A spokesman for Rizvi Traverse said the lawsuits were without merit.

By 2011, Mr. Rizvi had begun to realize major profits from his foray into Hollywood. He made a significant profit off the I.C.M. management buyout, according to two people with knowledge of the sale, and held onto a portfolio of back-end stakes in TV series like “Friends” and “The Simpsons” before selling them to another investment firm for $150 million. And in early 2012, Lionsgate Entertainment bought Summit for more than $400 million, generating a handsome profit for Mr. Rizvi, the people said.

To celebrate the Summit deal, Mr. Rizvi met a friend at New York’s Casa Lever restaurant, and over breakfast, surrounded by an impressive collection of Andy Warhols, Mr. Rizvi declared he was done investing in traditional media: He wanted to invest in companies that straddled media and technology.

By then, he had already begun acquiring shares in Twitter from Chris Sacca, a Silicon Valley angel investor and the founder of Lowercase Capital. The two met in 2006 at a party hosted by Mr. Branson on his Necker Island property in the Caribbean, according to a spokesman for Rizvi Traverse, and the two quickly became good friends and exchanged investment ideas.

In 2010, Mr. Sacca approached Mr. Rizvi with an opportunity. Evan Williams, one of Twitter’s founders, was leaving the start-up, and Mr. Sacca thought he could be persuaded to sell part of his equity in the company.