That's the risk you take in software in general. What stopped Instagram from copying Snapchat? Nothing. Micrsoft used to snuff out competitors in the office suite space all the time. MSN copied AIM. IE copied Netscape. It happens. You either work with founders you can trust or you don't.

Sure, but that doesn't mean that if you hire engineers who then screw you over you're a bad person and they're heroes.

For better or worse that is how it works.

And its not just with start ups. People who are more closer to work, generally tend to maximize returns for themselves above those are who are away from it.

This is true even in Big companies. Most product managers I know barely contribute anything to the product, most of the times its the engineers doing all the work and the product manager is just there to provide the validation 'This looks fine to me'.

There is a good reason why carpenters, plumbers, drivers, <skilled_worker> generally do better on the longer run than the supervisor ever does.

What if your game idea is half-baked, incomplete, and generally kinda crappy, the engineers realize you don't have a complete idea, but then go on and develop a fully-baked similar idea on their own later, and it becomes a hit?

Let's add some ambiguity to our "poor genius"/"brilliant thief" scenario :)

No I'd take the the court, because I wouldn't do that without a contract.