Could this pump have been caused by westerners trading on Huobi, who want to get their money out of the exchange by buying btc and transferring it to Stamp or whatever?
There are many possibilities. It could even be Chinese banks (and large holders) who have resources to take BTC outside China who are doing the buying. I think that by now most people with assets on Chinese exchanges will be working to get them out. Huobi and OKCoin etc. might move overseas, but what will they be worth after that move? Bitcoin speculation in BTC in China is dead in my opinion. If I had BTC on a Chinese exchange I would take them out ASAP. I could keep them i cold storage and hope for black market opportunities in China or I could try and dump them on a western exchange.