This isn't money laundering, this is something called "hawala", it's a way of moving capital using existing import/export markets. It just so happens that that market in this case is fentanyl precursors. Hawala is really cool actually, it's not that complicated (but still worth learning about), it basically boils down to "give that dude some money and take it out of what you owe me."

The money laundering that the drug cartels and Chinese are doing is completely different, and it's the acute reason that housing markets in London, Vancouver, Sydney and most big cities in the anglosphere are fucked to hell. The chronic reason, is, of course, the cantillion effect, but right now there's a shit ton of Chinese and organized crime money going into real estate, and for the Chinese part, the Chinese government has their capital controls but they allow it to happen because they exercise extraterritorial sovereignty over their citizens and know that the process gives them some sovereignty over assets in the west because their people own it. It also doesn't hurt that their rivals' populations becoming addicted to drugs elevates their relative position geostrategically.