Yes, but it's misleading to try to make it about the individual mortgages. The entire industry was engaged in very highly leveraged speculative investing. While individual people did buy more than they could afford, there was a lot of predatory lending and lying about the terms of loans. But meanwhile, the mortgages themselves, and what was effectively the insurance on the mortgages was being bought and sold in a ridiculously leveraged fashion, often by entities who were leveraging assets they no longer had (or that were no longer worth what they had previously been assessed by) with very little regulation.