I thought using Gaussian copula for CDO pricing was often regarded as being an important factor in facilitating the crisis?

there's a charitable way to read that, which is that they did ample statistical modelling/risk analysis of CDS and "concluded" they were safe enough to bundle mortgage debt under. Then you could sort of "blame math" (or the abuse thereof) in that circumstance. I know CDS is only like 1/10 chapters of the whole crisis, however.