volume is at historical highs in every exchange
Say what?? Historical highs for last 24 hrs maybe.
Volume at OKcoin was 429 kBTC on 2014-11-12, 609 kBTC on 2014-11-13. The previous high was 286 kBTC on 2014-03-05; typical volume for several months until 2014-10-03 (start of last recovery) was ~50 kBTC/day, and 110 kBTC/day in the few weeks until 2014-11-11.
The numbers at BTC-China on those two days were 371 kBTC and 508 kBTC. The previous high was 132 kBTC on 2013-12-07. Typical recent volumes were ~7 kBTC/day until 2014-08-13 (when they removed the trading fees?), then growing steadily to 90 kBTC/day by 2014-11-11.
The numbers at Huobi were more modest, 211 kBTC and 232 kBTC, against a previous high of 352 kBTC on 2014-02-25. Typical volumes were ~35 kBTC/day before 2014-10-03 and ~90 kBTC/day during the last recovery.
Bitcoin futures at BitVC (the international branch of Huobi) and "796" were also huge on those two days, on the order of 1 million BTC/day.
I have not looked at the other big Chinese exchanges that are not listed at BitcoinWisdom.
My best guess at what happened is still that statement by the OKcoin tech guy, that "a three billion euro hedge fund is going to be trading on our platform". Bitcoin news sites and many traders interpreted that as "the fund will start trading bitcoin", but there was no confirmation, and many were skeptical. To me, the words "on our platform" (rather than "at our exchange") mean that they will be using OKcoin's software and/or servers to trade their shares, not bitcoin. That would be great for OKcoin but irrelevant to bitcoin. If this interpretation is correct, it could explain why the price crashed right after the rally, and is now returning to the pre-rally levels.
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.
If the "hedge fund" explanation is correct, it may have been the most profitable misunderstanding in the history of bitcoin.