I answered this at length in a forum some months back and sadly can't find the text (for now).
The abridged version is: there too much money to be made.
Fentanyl has gone from direct primary import (which was blocked) to banning of exporting precursor drugs from bulk suppliers in China (to slow down | stop Mexican drug labs from mixing them to make Fentanyl) to where things are today ...
relatively mobile "popup" drug lab networks that start with bulk pre precursor drugs to make the precursor drugs that are funneled to final product labs.
It's a hell of a whack a mole game across Mexico, the USofA and Canada with a process that's tough to break, the initial drugs used are too useful for too many things to ban outright and the production aspect is broken down into many replaceable parts.
( I had references to most of those stages in the original comment, apologies for not having them to hand ).
The abridged version is: there too much money to be made.
Fentanyl has gone from direct primary import (which was blocked) to banning of exporting precursor drugs from bulk suppliers in China (to slow down | stop Mexican drug labs from mixing them to make Fentanyl) to where things are today ...
relatively mobile "popup" drug lab networks that start with bulk pre precursor drugs to make the precursor drugs that are funneled to final product labs.
It's a hell of a whack a mole game across Mexico, the USofA and Canada with a process that's tough to break, the initial drugs used are too useful for too many things to ban outright and the production aspect is broken down into many replaceable parts.
( I had references to most of those stages in the original comment, apologies for not having them to hand ).