... the markets got into trouble in 2007-2009. CDOs and CDSs became "artificial" and it became possible to go long or short a security that really didn't exist. Add that to the creation of "naked" credit default swaps (CDS) and more money was being bet (in the end, shorted) on things than the face value of the things themselves. Naked CDSs are pretty much gamblers bets. Because you aren't buying them to protect an asset that you have. And gambling commissions are much better placed to keep an eye on such markets. And whether a game gets thrown if too many bets are placed against it.
It's like me (and all your other neighbors) buying fire insurance on your house. When there's more money to be made by your house burning down, the invisible hand of the market moves so as to make that happen.