Why Twitter Shares Are Plunging Today

Twitter Inc. TWTR shares traded 5.15% lower in the pre-market session at $46.23 early Monday.

The plunge in the stock comes as the world's richest person and Tesla Inc. TSLA CEO Elon Musk declined a board position at the social media company.

What Happened: Twitter shares are tumbling following a tweet from CEO Parag Agrawal that said Musk had refused to join the company's board of directors on the day when his addition would have become effective.  The Tesla CEO had previously said that he hoped to improve the social media platform.

Musk was appointed to Twitter's board of directors last week — with his term expected to last until 2024 and an agreement that imposed a 14.9% limit on his stake — after recently acquiring a 9.1% share in the company.

The billionaire entrepreneur has continued to criticize Twitter as a platform in recent days. He asked his followers if Twitter was "dying," noting that most of the social media platform's top accounts "tweet rarely and post very little content."