UNITED STATES (AP) — Twitter co-founder Jack Dorsey has stepped down as CEO of the social media platform. He has been succeeded by Twitter’s current chief technology officer, Parag Agrawal.

Dorsey will remain on the board until his term expires in 2022.

In a letter posted on his Twitter account, Dorsey said he was “really sad…yet really happy” about leaving the company and that it was his decision.

Dorsey offered no specific reasons for his resignation beyond an abstract argument that Twitter, where he’s spent 16 years in various roles, should “break away from its founding and founders.” Dependence on company founders, he wrote, is “severely limiting.”

He expressed his confidence in Agrawal and new board chairman Bret Taylor, who is president and COO of the business software company Salesforce.

Twitter was caught up in the heated political atmosphere leading up to the 2020 election, particularly when it banned former President Donald Trump following his incitement of the January 6 riot at the US Capitol. Dorsey defended the move, saying Trump’s tweets after the event resulted in a risk to public safety and created an “extraordinary and untenable circumstance” for the company. 

Trump sued the company, along with Facebook and YouTube, in July for alleged censorship.

Critics argued that Twitter took too long to address hate speech, harassment and other harmful activity on its platform, particularly during the 2020 campaign.

“If he’s actually stepping away from Twitter this time, Dorsey leaves behind a mixed legacy,” said Paul Barrett, deputy director of the NYU Stern Center for Business and Human Rights. “A platform that’s useful and potent for quick communication but one that’s been exploited by a range of bad actors, including former President Donald Trump, who did his best on Twitter to undermine democracy — until Dorsey’s people finally had enough and shut him down.”

While Twitter has high-profile users like politicians and celebrities and is a favorite of journalists, its user base lags far behind old rivals like Facebook and YouTube and newer ones like TikTok. It has just over 200 million daily active users, a common industry metric.