I don’t think this is a moral panic article. There is a drop in seizures. What could cause that? The article goes into many possible causes: Maybe the cartels are sneaking it through another way, Increased border security, Crackdown on chemical precursors out of China, Turmoil within the cartel primarily responsible for smuggling it, Adulteration of the drug (including with a tranquilizer which might cause a behavior change which reduces consumption patterns), Opioid overdoses causing a drop in demand, Change in usage type (away from injection), Increased access to overdose treatment drugs, A demographic shift (younger people are less likely to be users)

Overall a well reasoned analysis of the possible causes.