John Cassidy explains:
There are basically five stages in Minsky’s model of the credit cycle: displacement, boom, euphoria, profit taking, and panic. A displacement occurs when investors get excited about something—an invention, such as the Internet, or a war, or an abrupt change of economic policy. The current cycle began in 2003, with the Fed chief Alan Greenspan’s decision to reduce short-term interest rates to one per cent, and an unexpected influx of foreign money, particularly Chinese money, into U.S. Treasury bonds. With the cost of borrowing—mortgage rates, in particular—at historic lows, a speculative real-estate boom quickly developed that was much bigger, in terms of over-all valuation, than the previous bubble in technology stocks.
As a boom leads to euphoria, Minsky said, banks and other commercial lenders extend credit to ever more dubious borrowers, often creating new financial instruments to do the job. During the nineteen-eighties, junk bonds played that role. More recently, it was the securitization of mortgages, which enabled banks to provide home loans without worrying if they would ever be repaid. (Investors who bought the newfangled securities would be left to deal with any defaults.) Then, at the top of the market (in this case, mid-2006), some smart traders start to cash in their profits.
Admittedly, Minsky’s theory fits the story.