"Confluence of events" might be correct.
If you look at the charts, it was setting up for a big squeeze. The 8,000 contracts which traded in that one minute bar does happen from time to time when the cash is open; it's not an unheard-of volume, neither was the volume in the bars preceeding the one in question. Volume was heavy at that time. However, normally, an 8,000 contract 1 min bar, doesn't result in 100 point moves. The depth was thin, people were wrapping things up, and the orders just chewed through the book until they found stop buy orders which cascaded and immediately triggered everything in sight.
Can someone tell me why you'd put stop buy orders (good til cancelled apparently) so far outside of the market, just resting there???? Swing traders? Who would do that?
I presume the arbs were working the differential which is why ES eventually came down so quickly, but 14 seconds is just too fast for the arbs to react to, but it is plenty of time for electronic execution to drive the market to the moon.
Probably alot of buy orders in anticipation of CISCO but without the usual depth on the sell side due to the impending market close.
Maybe the CME could introduce an dampening function which would prevent a bunch of similar orders from instantaneously shooting the market straight up- kind of like an order imbalance detector. (Since the person entering such an order would be the one to get burned, that would put a brake on such an undertaking.) But if the Chinese wanted to mess around with our financial systems, maybe this is a way.