At that point if you're motivated by more cash rather than not being seriously screwed, well, you don't sounds rational to me. That cash just doesn't have much value to you, and the risk does have cost to you.
The penalty here was disproportionate to the crime, sure, but Serge clearly took code owned by GS and uploaded it, without permission, to a 3rd party. Pretty cut and dry case of corporate theft here...
He was stupid. He should have made his intentions clear from the start, and he might well have simply gotten permission. As is, what he stole may well have been more akin to a using company laptop solely for personal use - certainly some kind of fraud, but probably also the kind of activity that the company might well have condoned if he'd only have asked.
Of course, without knowing what that code was and to what extent it was written on company dime, it's hard to say whether this was more like a bureaucratic oversight, a minor but intentional infraction, or a serious bit of fraud.
Regardless, it definitely sounds like Goldman really abused this guy. Keeping people in the dark about their true worth as negotiating strategy, and encouraging single-person whatever-works-goes work ethics (which may well be a form of intentional plausible deniability given the firms history) sounds to me like they treat their employees like exploitable resources.
So sure, I'd hope everyone would think twice before accepting a job offer there - because they clearly will stab you in the back when it serves them to do so.
In other words