While Billions isn’t entirely based on a true story, it is inspired by real events. For example, antagonist and United States Attorney Chuck Rhoades (played by Paul Giamatti) has been to said to be loosely inspired by Preet Bharara, who underwent investigations from 2009 until 2017 as the U.S. Attorney for the Southern District of New York.
While there isn’t a real Bobby Axelrod (the show’s main character and hedge fund manager played by actor Damian Lewis), he’s also loosely inspired by Steven A. Cohen, a real-life billionaire and hedge fund manager at S.A.C. Capital Advisors who was prosecuted by the Southern District of New York (he ended up pleading guilty to insider trading in 2013). The story of Steven has been said to have inspired the first season of Billions, which ran from January until April of 2016.
Many people on Wall Street think that Bobby is based on billionaire Bill Ackman of Pershing Square Capital Management, a hedge fund management company, due to the same initials, but Damian has said that’s not the case. “They say, ‘Ackman, Axelrod. They have the same initials.’ But Bobby Axelrod isn’t based on any real person,” he once told Page Six.
The second season of Billions premiered from February until May 2017 and has been said to have drawn inspiration from the Salomon Brothers 1990s treasury bond scandal.
Source : https://www.distractify.com/p/is-billions-based-on-a-true-story