What caused the financial crisis?

The column is titled "Three Trends and a Train Wreck."  I attempt to explain the financial crisis in as simple and general terms as possible.  Here is one paragraph:

Over all, then, the three fundamental factors behind the crisis have
been new wealth, an added willingness to take risk and a blindness to
new forms of systematic risk. All three were needed to bring about the
scope of the current mess – so that means we’ve had some very bad luck
on top of everything else.

I have about nine hundred words to flesh this out and to discuss Fischer Black as well; Black is a neglected but insightful macroeconomic theorist who starts with ideas from finance.  Here is another paragraph:

Subprime loans collapsed first because those were the investments most
dependent on relatively poor borrowers who were the most likely to
fail. Since then, we’ve seen asset values fall throughout the economy.
Subprime borrowing was the canary in the coal mine, but it was hardly
the only problem. It now seems that a wide range of asset prices were
artificially inflated. The market for contemporary art, which depends
almost exclusively on very wealthy buyers, will probably be the last
market to plummet but that development is almost certainly on its way.

One thing to keep in mind is how international the crisis has been; any explanation should start there.  I wish in the column I had had space to discuss Spain, which has had relatively prudent banking regulation but still will have one of the biggest downturns in Europe.  It is also worth considering Norway, Canada, and some of the other countries which limited their risk exposure all along.  I mention Japan, but Brazil and Mexico also already have their banking crises behind them in the former decade and they too form other valuable points of comparison.

I am not sure I understand this Daniel Davies post, but it may have some overlap with my arguments.

Addendum: You might want to read this Jacob Weisberg column saying that the financial crisis refutes libertarianism.  His paragraph starting with "There’s enough blame to go around…" is exactly the foil I had in mind.  His overall thesis is worth pondering but he doesn’t once consider any cross-sectional variation across nations; such consideration wouldn’t help his thesis.  Am I allowed to say that the experience of Iceland refutes the small nation, social democratic model?  Probably not, nor should I be.

Second addendum: Tim Harford has a humorous piece comparing the crisis to Monopoly the board game.