Kate Conger and Lauren Hirsch

The world’s richest man closed his blockbuster purchase of the social media service, thrusting Twitter into a new era.

Bret Taylor, an understated executive, led talks with Elon Musk over his plans to acquire the company and the legal fight to seal the deal.

The billionaire’s surprise move came months after he tried to back out of a $44 billion deal to acquire the company.

The question of whether Elon Musk must buy Twitter, as he agreed to do in April, is headed to a court in Delaware.

In a regulatory filing on Friday, Mr. Musk said Twitter was in “material breach” of the acquisition agreement.