Why in the world do we have so many scammers around?!
I don't know the specifics of any of these guys, but my guess it that it's because people are too quick to hand over their money when someone claims to be offering massive returns.
I think it's unlikely that very many of these guys (if any) set out to be scammers, but I have to imagine it's a lot easier for a GP to fall into these schemes when he has a project failing and investors to answer to. At that point the GP is already like a deer in the headlights.
In many of these investments, the numbers on the proforma are only half the story. The people executing the plan are equally- if not more- important. If the Team page in a guy's pitch deck isn't strong or doesn't check out, don't invest. If a guy hasn't been doing this for a long time*, don't hand him your money, and then he won't become a scammer.
None of this is an excuse for a GP to resort to fraud if he's in trouble, but if we're going to learn a lesson from these blowups, this might be it.
*Yes, obviously everyone has to start somewhere, and everyone needs a first investor. But that "somewhere" should be after he has many years of experience in said industry. And those first investors should understand their risk, and maybe get a better deal in exchange for it. They certainly shouldn't be people who are handing over all their life savings, or mortgaging their house to invest with the newbie.