Even after all that has been said and written, people are still searching for a narrative to explain how a relatively small number of homebuyers failing to make mortgage payments led to such a deep recession. The 22-page Securities and Exchange Commission complaint against Goldman Sachs & Co. provides an outline of such a narrative.

It has big players: Goldman Sachs and Paulson & Co.—not the former Treasury secretary, the hedge fund that famously made a winning bet on the collapse of the housing market. It has an alleged villain...