He beat Elon Musk in court once. Sam Altman hired him to do it again.

From the source

Elon Musk, William Savitt and Sam Altman Getty Images William Savitt is representing Sam Altman in Elon Musk's lawsuit trying to dismantle OpenAI. Savitt, a top lawyer at Wachtell, went up against Musk before in a dispute over Twitter. He was a cab driver, rock band singer, and Supreme Court clerk before becoming a litigator. When Sam Altman needed someone to beat Elon Musk in court, he hired a lawyer who had done it once before: William Savitt. Savitt was a natural choice to take the case. For decades, he'd occupied the upper echelons of corporate litigation. He represented Twitter in 2022, suing Musk to force him to go through with his purchase of the platform. His law firm, Wachtell, Lipton, Rosen & Katz, worked on the complex restructuring of OpenAI's for-profit arm.