It's the fault of the rocket scientists (they mean former string theorists)! They devised these complicated ways of lending money to people who couldn't afford to pay that nobody could understand!
What bullshit. The problem was conflict of interest. Guys were getting rich selling pigs with lipstick. The string theorists just applied the lipstick.
It's really just the usual story. Managers with a conflict of interest mismanaged other peoples money - managed to put a bunch of it in their own pockets.