Oh, this is a goody:

In a time of state-sponsored easy credit all projects get financed by incautious banks with cheap, centrally supplied money. There is no market for cautiously lent money, priced correctly for the risk involved. Why would anyone pay more for funds from a cautious bank when cheaper funds from an easier source are available?

This is why the profits of incautious banks grew, and why their stock prices multiplied.

Meanwhile careful bankers sunk. As Brown (and Greenspan) injected ever more money into the economy the cautious banks began to lose their customers, their managers, their share values, and their independence. This Darwinian extinction of caution is the direct result of a monetary environment which was hostile to cautious bankers; one which favoured those banks with an appetite for cheap money.

Paul Tustain, How Bullion Vault sees the credit crunch (email to Bullion Vault customers)

That is the best explanation I have heard so far as to why the money men went mad: the government made them.  And, yes, I am a customer of these people.