This is a good discussion of usury we've had. Let's stick with it a bit.
Proposed, that usury really ought to be seen as an offense against property. According to the Angelic Doctor usury is unjust because it is "to sell what does not exist." Now what does not exist cannot have property. Therefore usury (in our current case) may be understood as to offer property in nothing. It is to trade fraudulent property.
At best what the exotic finance engineering of Wall Street did was trade in property in something that did not yet exist. That is, at best this exotic finance assumed a temporal projection was accurate with undo certainly, and on that basis converted future potentials into contemporary abstractions. We may charitably say that the element of fraud is lessened because the aggravating element of intent was not supplied. They were most of them mere fools, not criminals.
They were usurers. And since durn near every last one of us was invested in a fraction of the usurious economy, in some fund or account somewhere, the blame falls in a widespread pattern indeed. They is we.