Tesla CEO Elon Musk won't be joining Twitter's board of directors as previously announced. The tempestuous billionaire remains Twitter's largest shareholder.

Twitter CEO Parag Agrawal tweeted the news, which followed a weekend of Musk tweets suggesting possible changes to Twitter, including making the site ad-free. Nearly 90% of Twitter's 2021 revenue came from ads.

"Elon's appointment to the board was to become officially effective on 4/9, but Elon shared that same morning that he would not be joining the board," Agrawal wrote in a reposted note originally sent to Tesla employees. "I believe this is for the best."

Agrawal didn't offer an explanation for Musk's apparent decision, although he dropped one major hint. The Twitter board "believed having Elon as a fiduciary of the company, where he, like all board members, has to act in the best interests of the company and all our shareholders, was the best path forward," he wrote.

At 9:30 p.m., Musk tweeted an emoji of a face with round eyes and a hand over its mouth. The symbol is often used to suggest embarrassment or coy laughter, sometimes with a connotation of "Oops!" It was not clear what Musk meant by the tweet, and he didn't elaborate on it.