Billionaire David Rubenstein told us why he paid $1.7 billion for a baseball team, and shared his 2 biggest investing mistakes

Billionaire David Rubenstein told us why he paid $1.7 billion for a baseball team, and shared his 2 biggest investing mistakes David Rubenstein is the principal owner of the Baltimore Orioles. Chris Bernacchi/Diamond Images via Getty Images David Rubenstein explained why he bought a baseball team, missed out on Amazon and Facebook, and would be careful betting on or against the AI boom.The billionaire cofounder of Carlyle Group, one of the world's biggest private equity firms, spoke to Business Insider ahead of the release of his new book "Inside the Owner's Box: Conversations on Power and Leadership in Sports."In the book, Rubenstein tells the story of buying the Baltimore Orioles for around $1.7 billion in 2024, and shares his interviews with fellow team owners, including Robert Kraft of the New England Patriots.He told Business Insider that a few decades back, the ultrawealthy didn't want the scrutiny that comes with owning a team. But changing attitudes and soaring valuations mean they now believe "not only can they have some fun, and kind of be a big deal in the sports world, but they can actually make money on it."Rubenstein said he bought the Orioles because he hadn't done much on the philanthropy front for his hometown of Baltimore, so he wanted to "try to do something for the city."Early mistakesHe also shared that his best investment was likely "starting Carlyle with hardly any money," while his gravest investing error was "walking away from Facebook and Amazon at the beginning."Rubenstein said that Amazon's founder Jeff Bezos, gave him and his partners at Carlyle a stake in the e-commerce startup "at the very beginning." But they decided to sell it after Amazon stock collapsed during the dot-com bubble, meaning they dumped a position that would have been worth "many billions of dollars today."He also recalled that his then-future son-in-law was a classmate of Mark Zuckerberg, and asked Rubenstein to invest when the Meta cofounder was seeking to raise $30,000 to launch his website."I didn't take it seriously," Rubenstein said. Eduardo Saverin provided the initial capital for Facebook instead, and now ranks among the world's 60 wealthiest people with a roughly $40 billion net worth, per the Bloomberg Billionaires Index. Navigating the AI raceRubenstein told Business Insider that AI company valuations are "really, really high" and hard to justify with earnings in some cases. But he pointed to Nvidia's recent blockbuster results as evidence that it's "not all pie in the sky.""As we learned in the dot-com era, not every dot-com company survived and made money, and not every AI company will survive and make money," Rubenstein said."But the ones that are hot and are doing well now, probably will continue to do well for some time," he added.Rubenstein also acknowledged concerns about aggressive accounting, circular financing, hidden debt, and overinvestment in AI. Quoting Warren Buffett, he said that "when the tide goes out, we'll see who's been swimming without a bathing suit."However, Rubenstein also emphasized that markets have historically rebounded after crashes, meaning the "biggest mistake people make when you have these bubbles bursting is selling everything and getting out."Instead of joining in the panic-selling, he said, "probably that's the time to hold on and maybe buy more." Read next Theron Mohamed is a London-based correspondent on the International team at Business Insider. His coverage spans finance, investing, wealth, markets, and the economy.Theron joined BI in 2019 as a reporter at Markets Insider and rose to the rank of correspondent before moving to the Trending team then the broader International team. He previously covered tech, media, and telecom stocks for Investors Chronicle magazine and had a brief stint on the Financial Times' Data team. He interned at the Wall Street Journal in New York where he primarily wrote for Heard on the Street.Theron has freelanced for The Independent, The Telegraph, WIRED, and several smaller publications. He holds an undergraduate degree in geography from the London School of Economics, and a master's degree in journalism from Columbia University.Theron often covers Warren Buffett, Michael Burry, and other elite investors. He also writes about the world's wealthiest people and shares financial advice from all manner of rich and successful people.Email Theron at tmohamed@businessinsider.com and follow him on X @theron_mohamed. Finance Billionaires Private Equity More Amazon Facebook Investing AI Stocks Mark Zuckerberg Jeff Bezos