Elon Musk, who spent the weekend tweeting about how Twitter is dead, has decided not to take his seat on the social media site’s board of directors. The Tesla CEO was named to the board last week after snapping up $3 billion worth of stock, making him the company’s largest stakeholder. But, according to Twitter CEO Parag Agrawal, the appointment was contingent on “contingent on a background check and formal acceptance.” On Saturday, the day his term was supposed to start, Musk backed out. “We were excited to collaborate and clear about the risks,” Agrawal said in a statement just before midnig…