The simple explanation is the market had adjusted to the possibility of China locking out bitcoin well before the 15th. When there is public information about some big event in the future it will always be priced in well before the date. Anyone who decides to trade such news on the day of is an absolute fish and should stop trading.
Not true. The market moves leaps and bounds on news. This "it's priced in" stuff is a pipe dream.
Sorry but it is true. Though you are right too, the market DOES move leaps and bounds on news... when it is reported, not when it takes effect. Byron was saying basically the same thing, the market moves on news/rumor, not WHEN the news/rumors subject is supposed to actually happen.
Thus people knew China was going to mess with exchange banks and new rules would take effect on the 15th. The market priced this in before the deadline because everyone knew it was coming and everyone wanted to take advantage before others... which all happened BEFORE the 15th.