This is oversimplifying too much IMO. Obviously the potential reward working at startups is much higher than megacorps, and you can very safely say that people working at startups have a higher risk appetite. However, plenty of people work 9h-12h a day (say, at Meta) in wish to get promoted at rocket-speed and play to "win" the higher TC at megacorps, and it happens often enough that very-driven people do join megacorps.