So, to recap: Elon Musk bought 9% of Twitter's shares, and in the process violated disclosure rules (you have to publicly disclose within a certain amount of time that you've acquired more than 5% of a company's shares, and Musk waited a week too long; this kept stock prices low so he could keep buying).
He believed that Twitter would agree to make him CEO or Chairman based on this purchase, since he was the single largest shareholder.
When they instead just offered him a seat on the board, he threw a tantrum and offered to buy the whole company outright, pushing the stock price up so that when he sells his shares in a fit of pique, he'll make more money.
