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- Planet Fitness' board of directors asked its CEO Chris Rondeau to step down last week.
- Shares tumbled nearly 20% following the news.
- Rondeau told Insider he was "blind sided" by the board's decision.
Former Planet Fitness CEO Chris Rondeau told Insider he didn't know why the company's board of directors asked him to resign last week, a move that sent Planet Fitness shares tumbling nearly 20%, shaving over $1 billion in market cap off the US's largest network of gyms, down from $5.2 billion to $4 billion in less than a week.