The CEO and COO cashing out 500,000 shares each sounds like some kind of prisoners dilemma. What do you do with your shares if you’re an employee at this point? I’d dump half I guess and cross my fingers.
Even if you are bullish long-term, it makes sense to cash out while it's overbought and buy back later.
Also, keep in mind 500,000 shares might sound like a lot to us, but it's not even close to a majority of their position.
Looking at this as a signal as to whether you should hold as an employee would be silly.