This story  and its experts do not address the event well.

This was the first instance of trading strategy designed to reduce risk changed the distributions in which it expected to traffic.

Portfolio insurance is a model that buys stock index futures when the index rises and sells when it drops.  In 1987 the model was completely mechanical and kept selling through the day.  At one point the futures were down almost 15% more than the stocks as a bunch did not open.

Interestingly portfolio insurance gave was to TAA in the 1990 that muted market volatility for a decade until it fell out of favour.

Likewise. 1998 was a similar event where quantitative risk management and arbitrage trading induced similar results in spread trades, ultimately taking out LTCM at its epicenter. 

Even 20078 can be presented as a risk model based crisis.

Understanding market structure is a key to successful investing, but it is a topic poorly understood.  The best academic work is by Richard Bookstaber.