Musk tweeted Tuesday that he was "looking forward to working with Parag & Twitter board to make significant improvements to Twitter in coming months!" And Twitter founder Jack Dorsey said that Musk and Agrawal would make "an incredible team." Twitter's stock surged after his initial purchase was disclosed.

As part of his agreement to join the board, the Musk had committed to not acquiring more than 14.9% of the company's shares during his term. Some corporate governance experts suggested that the move could have been a way of reining in Musk's influence over the company. Now, that limitation is no longer in place, leaving the door open for Musk to potentially take a more aggressive stance by buying up more of Twitter's shares.

In his tweet Sunday night announcing Musk's reversal, Agrawal said the company's board had "believed that 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."

"In our opinion, the Twitter Board and Musk could not come to an agreement around Musk's communications with the public (various polls) over Twitter as he likely needed to take a more back seat/quiet stance as part of joining the Board," Wedbush analyst Dan Ives said in an investor note Monday. He added that Musk's relationship with Twitter may now become "a 'Game of Thrones' battle between Musk and Twitter with the high likelihood that Elon takes a more hostile stance towards Twitter and further builds his active stake in the company."

It's not entirely clear what changes Musk was — or perhaps still is — seeking for Twitter. In recent weeks, Musk suggested on Twitter that the platform does not allow free enough speech, and said it should make its algorithm open source. He also polled his followers last week about whether they "want an edit button," a longtime feature request, if a divisive one, from many Twitter users. (Twitter said last week it has been working on an edit feature for the past year.)