You don't need to invoke conspiracy theories here: the trade is vastly profitable and that's what's driving it. If China cracks down (in reality, not just on paper), production will just shift to India or Vietnam or wherever.
For what it's worth, China as a whole (both the people and the government) remember the Opium Wars quite well and are thus strongly anti-drug: stats are thin on the ground, but by all accounts drug offenses are the top reason for the death penalty. Of course, it only take a few factories to churn out vast quantities of the stuff, and the profits are sufficient to lubricate any officials who might otherwise object.
For what it's worth, China as a whole (both the people and the government) remember the Opium Wars quite well and are thus strongly anti-drug: stats are thin on the ground, but by all accounts drug offenses are the top reason for the death penalty. Of course, it only take a few factories to churn out vast quantities of the stuff, and the profits are sufficient to lubricate any officials who might otherwise object.