Weren't the banks selling each other credit default swaps they couldn't cover, such that the moment a single bank went under it triggered the collapse of the en

Weren't the banks selling each other credit default swaps they couldn't cover, such that the moment a single bank went under it triggered the collapse of the entire banking system? Blaming the mortgage lending is like saying, "I didn't blow up the neighborhood with my unsupervised warehouse full of explosives, it was those damn kids playing with matches!"