That was indeed a mistake in many levels. Nevertheless, China is responsible of China’s pollution output, nobody else. Unlike you seem to imply, the chinese are not unthinking animals, but regular people – with even higher than average IQ compared to west according to some studies. They were perfectly capable of making good decisions instead of bad ones.
And in fact, they seem to be in the process of making such good decisions now. The Economist believes that their CO2 levels will peak this year and start to go down in the near future due to China’s investments in clean energy.