Suddenly, Tesla's Elon Musk is Twitter's biggest stakeholder

Tesla CEO Elon Musk acquired a 9% stake in Twitter to become its largest shareholder, just before raising questions about the social media platform’s dedication to free speech.

The ultimate aim of Musk's 73.5 million share purchase worth $3 billion based on the closing price Friday, is not clear. Yet in late March Musk, who has 80 million Twitter followers and is very active on the site, questioned free speech on Twitter and whether the platform is undermining democracy.

The regulatory filing Monday says Musk bought the shares on March 14, describing him as a long-term investor looking to minimize his buying and selling of the shares. That means that Musk acquired the shares before beginning his public discourse on the First Amendment and Twitter.

Yet Musk has also raised the possibility, publicly before his massive and loyal Twitter following, of starting a rival social media network.

Industry analysts are skeptical about whether the mercurial CEO will remain on the sidelines for long.

“We would expect this passive stake as just the start of broader conversations with the Twitter board/management that could ultimately lead to an active stake and a potential more aggressive ownership role of Twitter," Dan Ives of Wedbush Securities said in a client note early Monday.

Twitter's stock surged more than 22% at the opening bell Monday. The company did not immediately respond to a request for comment.

Musk told his more than 80 million followers on Twitter that he was “ giving serious thought " to creating his own social media platform and has clashed repeatedly with financial regulators about his use of Twitter.

His Twitter stock purchase comes as Musk is locked into a bitter dispute with U.S. securities regulators over his ability to post on Twitter. Musk’s lawyer has...