I think you discount the idea that margin trading can be manipulated by a crowd and not by simply one bad actor. Why must one whale drop it so low? 

Surely, a whale might aspire to such an amazing play, but what is more likely is that a series of crescendoing series of whales took advantage of each other's plays.

Whales are trading with the API and making trades in a fraction of the time it takes one to manually enter. 

Sure there could be a number of mitigating side effects creating a perfect storm scenario. I think this might remain a bit of a mystery for some time.