It is fairly normal to sell a portion or all of shares received from excercising stock options to cover tax liabilities. I don’t think it’s clear that knowledge of the exploit changed his behavior. Furthermore the stock has not taken a major hit on the news. It is still up compared to a month ago, 3 months ago etc. it is down a little over the last week. The idea that he sold to avoid a stock crash doesn’t really hold if the stock didn’t crash, right?