I don't think the FBI doesn't have to do with it. It is because that they also know what the risk of investing with those kinds of investment.
And they can't really run after them just to chase the people behind hash ocean.
Just learn the lesson from that incident.
even though the FBI would care about it and about cyber crime, and even though they would managed to caught them, there would be no chance people to take their money back.. so it's all pointless..