https://en.wikipedia.org/wiki/Illegal_drug_trade_in_China
It's like saying you're gonna stop all the drug dealers in US to stop selling drugs, its very hard for China to stop all narcotics.
Heres an official report by the US-China Economic & Security Review Commission on Chinese Fentanyl Production: https://www.uscc.gov/sites/default/files/Research/USCC%20Sta...
and I quote: "China is a global source of illicit fentanyl and other NPS because the country’s vast chemical and pharmaceutical industries are weakly regulated and poorly monitored...Chinese law enforcement and drug investigators are unable to effectively regulate the high volume of drugs and chemicals the country produces.In many cases, the chemicals used to produce fentanyl and fentanyl-like products are illegally diverted from legitimate pharmaceutical uses, with criminals taking advantage of inadequate enforcement protocols to produce unregulated chemicals and NPS. Until 2014, a regulatory loophole allowed Chinese chemical companies to operate in a gray area of oversight, freeing them from inspection requirements and other certification systems. That loophole was closed in 2014 when China’s State Administration of Work Safety implemented new regulations on chemical production to improve management of nonpharmaceutical businesses, including enforcing stricter licensing requirements. Even under the new regulations, Chinese pharmaceutical and chemical companies continue to divert chemicals from legitimate pharmaceutical uses and adulterate legitimate pharmaceuticals during production.This makes drug enforcement within China difficult, as many manufacturers of fentanyl and other NPS are legitimate companies legally producing chemicals. Although some of these chemical manufacturers knowingly ship their products to the United States for illicit purposes, Chinese chemical and pharmaceutical exporters continue to operate with little oversight"
Do not get me wrong, I've seen the impact of Fentanyl and I want China to step up on crushing its production.