First, the stock market was richly valued. Some would say "fully" valued, but that means that there is a "correct" valuation for the markets, and everything lower than that is "wrong." I don't look at the market that way. On the basis of future earnings, the market was richly valued.

Second, the bear market has been prowling below the headlines for almost eight weeks now. Small caps and non-headline names have been selling off consistently, week after week. The small caps are already in an official bear market (down 20%+).

Third, the indexes are cap-weighted, which means that the largest companies in the DJIA and SP500 can hold up the indexes for a long time as the smaller components get weak and start flat-lining or selling off modestly. Then when the big companies finally get taken down, it looks like a much more rapid drop.

The Fed has indicated that they were going to taper their bond buying program on schedule, which is about $75B/month of extra liquidity taken out of the markets. Europe's monetary indicators are showing a slump towards deflation, and the ECB isn't going to do much about it.

The dollar is strengthening, which will take down the indexes all by itself.

And then there's all the exogenous issues you mentioned. Right now, I think the lack of leadership in the west is starting to cause traders to look at the situation and think about "risk off" trades.