There was much to celebrate last spring when Ariel Emanuel, the chief executive of the talent agency Endeavor, helped throw a splashy Hollywood party for Saudi Arabia’s crown prince, Mohammed bin Salman.

The soiree, with guests including the Disney chief executive Robert A. Iger, the Amazon founder Jeff Bezos and the former N.B.A. star Kobe Bryant, took place as Saudi Arabia’s government investment fund was completing an agreement to invest $400 million in Mr. Emanuel’s firm. The deal was meant to finance Endeavor’s growth, while diversifying Saudi Arabia’s economy via the talent agency’s work in sports, events, modeling and television and film production.

Less than a year after the star-studded party, Endeavor and Saudi Arabia have gone through a messy breakup, set in motion by the murder last October of the Saudi journalist Jamal Khashoggi.

In recent weeks, Mr. Emanuel’s firm returned the $400 million investment, effectively severing Endeavor’s relationship with Saudi leaders, according to two people with knowledge of the transaction.