> They then elect a board of people who will approve whatever they want.

As others have mentioned, Twitter has a staggered board, meaning not all board members are up for election at the same time. Replacing the board would take years in a hostile takeover.

Patrick Boyle did a great video on this which is slightly less relevant now that the board has accepted the offer but still is a reasonable intro to corporate governance:

https://youtu.be/QXxeyOVpnCU