Last week, Elon Musk became Twitter's largest shareholder. The Tesla and SpaceX CEO was going to join Twitter's board — then he wasn't.

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"My offer is my best and final offer and if it is not accepted, I would need to reconsider my position as a shareholder," Musk said

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(He holds more than 9% of Twitter's shares.) "Twitter has extraordinary potential. I will unlock it," Musk added.

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"I invested in Twitter as I believe in its potential to be the platform for free speech around the globe, and I believe free speech is a societal imperative for a functioning democracy," he said.

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In a statement, the company said its board "will carefully review the proposal to determine the course of action that it believes is in the best interest of the Company and all Twitter stockholders."

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[{"selector":"#anim-287f662c-35bc-4349-bff2-b94b4781c92e [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":3500,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-0e809b45-5a56-4074-90b2-b2103e07bfb2","keyframes":{"opacity":[0,1]},"delay":0,"duration":4000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-ea72bd7b-ee55-4cce-ad1b-aacca70934d7","keyframes":{"transform":["scale(0.3333333333333333)","scale(1)"]},"delay":0,"duration":4000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] Musk's offer of $54.20 per share is 38% more than the value of Twitter stock the day before his investment was publicly announced and it's 18.2% higher than Wednesday's closing price.