“When @elonmusk and I first spoke of his vision for X, I knew it would be the opportunity of a lifetime to carry out the extraordinary mission of this company,” Yaccarino wrote. “I’m immensely grateful to him for entrusting me with the responsibility of protecting free speech, turning the company around, and transforming X into the Everything App.”

X owner Elon Musk replied, “Thank you for your contributions,” and has not made any other comment about the future of the CEO role at X.

While Yaccarino was not candid about her reasons for departing her role, she made her announcement mere hours after X’s AI chatbot, Grok, was taken offline after going on an antisemitic tirade. Her departure also comes on the same day that Musk is supposed to reveal Grok 4.

Yaccarino joined the company just months into Musk’s ownership, leaving her longtime role as chairwoman of global advertising and partnerships at NBCUniversal.

Given her stature as an advertising executive, Yaccarino was brought in as X CEO to maintain relationships with advertisers amid a massive shift in platform leadership when Musk bought Twitter.

Her job was not easy. Within the first six months of her tenure, Musk used his personal X account to endorse the antisemitic “great replacement” conspiracy, as well as other debunked conspiracy theories like Pizzagate. He went on to sue nonprofit research groups like Center for Countering Digital Hate and Media Matters, which published a report that highlighted X’s display of extremist content beside advertisements for companies like IBM and Apple, leading them and other major advertisers to depart the platform.

While Yaccarino presumably tried to mend relationships with advertisers, Musk continued to complicate her efforts. Onstage at the DealBook conference in November 2023, Musk was asked about these pauses in advertising, to which he replied, “Go f— yourself,” then waved to the audience and said “Hey, Bob,” referring to Disney CEO Bob Iger, who was in attendance.

Musk apologized for these remarks, and Yaccarino stood by him.

“X is enabling an information independence that’s uncomfortable for some people,” she said at the time. “We’re a platform that allows people to make their own decisions. And here’s my perspective when it comes to advertising: X is standing at a unique and amazing intersection of Free Speech and Main Street — and the X community is powerful and is here to welcome you.”