If you were middle aged you might just decide to up and leave your job if it was for a company which was going nowhere, backwards or just nowhere too exciting. The thing is, you're spruiking AEB as a company on the verge of something amazing. That's not compatible with your other suggestion of someone just deciding to leave for no big reason. He may not be a founding director, but he is (was) still a director in a more senior, well paid position than most people ever achieve. People don't get to that position by being apathetic about work, it would be very unusual for someone to say "Hey, I've just out of the blue decided that despite working really hard and tenaciously all my life, and having a job as a director of a company about to hit the really big time, I'm just going to walk away and go fishing". He wasn't the cleaner or boilermaker or field laborer or the sparky wiring up the shipping containers. Heck, even if I was just a grunt level award wage worker on a project like this and I believed it was on the verge of what you claim, I'd be sticking around on minimum wage just to watch (unless I was offered a real job somewhere else).
AEB Price at posting:
24.0¢ Sentiment: Sell Disclosure: Not Held