The short answer is that the Europeans (maybe for some of the reasons given in this article), were greedier than the Chinese.
It's likely that the Chinese empire reached the New World before Columbus. http://www.economist.com/node/5381851. But the thought of enslaving an entire population and stealing all their natural resources didn't even occur to the Chinese explorers. Whereas the Chinese expeditions were financed by the empire, the Europeans expeditions were financed by debt, so the men needed to arrive on land and quickly acquire wealth for themselves at all costs, or else they would return to Europe broke or never return at all. And this led them to commit the horrendous acts in the New World we know so much about.
Western Europe, now full of gold and silver stolen from the New World had levels of wealth it had never experienced. This led to increased demands for certain goods (like English wool), which forced the population off of the land and into urban centers, thus creating the landless working class. This process was called The Enclosure https://en.wikipedia.org/wiki/Enclosure. An urban, landless working class, was a necessary condition for the industrial revolution. The extraordinary wealth ready to be invested in industry, a product of colonialism and the slave trade, was another necessary condition for the industrial revolution.