Whatever the cause, this 3-day rally and crash generated trades totaling over 1 million BTC at OKCoin, several million BTC overall. The exchanges must have collected several million dollars in fees and interest, and arbitragers (possibly the exchanges themselves) must have made many millions too.
In that paragraph I was not including the futures' markets like BitVC and 796.com (which, IIUC, are the only ones doing double-counting). But the volumes during those two days were huge either way.