I have no doubt that mortgage fraud played a big role. But what I am suggesting is that monetary policy could fuel an asset bubble simply by increasing available credit by pinning down rates. No doubt, relaxed lending and fraud would only exacerbate this, which I'm sure it did.
Yes, I suspect that is possible, but then my theory of asset prices is that people have a bias toward the status quo, and the perception of change ("new information") makes people think prices should change, so they proceed to change prices. So there is a question about how much policy rate changes are just due to this sort of circular reasoning ("something should be happening, so let's do something!") versus actual changes to the availability of credit. That being said, the real skepticism here is whether monetary policy can be used to stop an asset bubble once it's started.