Quote from nonlinear5:
Yes, that's the explanation. The key is not to think of 75,000 contracts as percent of daily volume, but as percent of the total liquidity available during a particular period of time, such as the period of 20 minutes or so during which these contracts have been sold. See the details here: http://sec.gov/news/studies/2010/marketevents-report.pdf
Notable part of the report: "By 2:45:28 there were less than 1,050 contracts of buy-side resting orders in the E-Mini, representing less than 1% of buy-side market depth observed at the beginning of the day".
Right on, this is the key issue here, the order book was in a very illiquid and unstable state when the 75k order hit. People are paying to much attention to the order and not the market it was sent into.