The article confuses two related but separate questions. The first is who caused the collapse. The second is whether or not they did something illegal. On the first point, the article claims the banks are "not guilty", which isn't really true. They're excessive risk-taking did cause the collapse. That doesn't mean it was necessarily illegal, just that they are "guilty" of causing the collapse. But just because the causes weren't illegal doesn't mean that they didn't commit fraud along the way. The collapse revealed the fraud that had been going on, and while it didn't cause the collapse, it made it worse.

Ultimately, it doesn't even matter whether there was a collapse or not. The fundamental point of people like Ferguson is that we now know of a number of illegal acts which took place before and during the collapse, yet those have not been properly prosecuted, and that's a problem.