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.
I love a good conspiracy as much as anybody, but it really would not take a genius, nor a whale, to simply set a lowball buy offer. So far, nobody has produced a record of a 30 million dollar transaction, but we do have the Genesis transaction, started 30 minutes before the crash, and it's a pretty sure bet that they are on the backbone.
This looks like an unforced error to me.