Donald Knuth wrote that "premature optimization is the root of all evil." I don't know exactly what he meant, but if he meant what I think he did, I agree. Translate "premature" into "partial" or "short sighted" and you'll get the idea. Capitalism optimizes prematurely, for the part, the private interest, at the expense of the whole, the general human interest. Yes, finance was "rational" in a sense, but in a very partial, short sighted sense. But then you have to reconcile the parts at the global level. And that's when it was shown how botched their "rationality" was.