The thing that delayed my recognition for so long, is the fact that these guys have so much money already - why would they need to steal more? Any credible ideas?
If you are shorting the market, then it does not matter how much money you collected in fees.
Let's say they started shorting back in 2011, can you imagine how much underwater they would be with BTC at $500.
Selling customers BTC that you don't already own can be a recipe for bankruptcy.