Because people overestimate the amount of Chinese bitcoin holders. Their only measure of adoption in China are the trading volumes which is ridiculous because chinese exchanges have 0% fees vs western exchanges which have more than 0.20%. They try to compare chinese vs western exchanges and conclude that there is a large number of chinese holders. However, the community rarely points this out and so I think people are just really overestimating. This is evident when BTC China raised their fees. Suddenly it looked like a ghost town. You can just look at this and decide for yourselves how overly exagerated the volumes are before BTCchina raised fees.
https://bitcoinwisdom.com/markets/btcchina/btccnyIs there a coinmap.org for China? How is the merchant adoption there? How large is the chinese bitcoin community and where is it?
You see, it is hard to tell and we could only look at the trading volumes which is extremely misleading. The bitcoins just go back and forth to the same people which gives the impression of high volumes and then people outside China think China is such a big player.
It may also be possible that the market is repricing the world of Bitcoin without the other 1.3 billion Chinese, approximately 19% of the world's population. The price is now down 62% from mtgox and China. Will it go any lower? Possibly but I doubt it will be further down. The numbers just don't add up.
The third point I'd like to make is that people attribute the run up to China when in fact there are more significant events that caused the last bubble. These include the "cleansing" Bitcoin gained after the Silk Road bust and the official US Senate hearing which was a huge event to clear up legitimacy of Bitcoin. All eyes were on Sen Carper which turned out to be really positive and then prices got really crazy.