for such brilliant minds, why not build something legit?"
For starters building a good stuff is not so easy and it is easier to feed on people's greed.
I once read that one of the 31 reasons why people fail is that the expect something for nothing.
The more people keep acting this way, the more they will keep losing money.
I will talk about the biggest scam in history that was conducted by a Nigerian and analyse.it.
Doing things right like you said is obviously slow and requires work but also being a very successful scammer, it requires work.