As Molly Cernicek and I have pointed out before, the "market" in nuclear secrets and material seems to be largely driven by government stings. So Leonardo and Marjorie Mascheroni allegedly wound up trying to sell secrets to US, not Venezuelan, government agents. Presumably the government of Venezuela knew nothing about it, or cooperated with the US government if it did.
No real market there.
And Molly and I hope to have another in our series "Profit, Loss, and Proliferation" posted in the next day or so.