In the paper, they describe that they effectively use sort of mules to deposit cash into their own bank accounts. So the cash is split distributed and then needs to come back. The paper is showing that crypto is being used to consolidate it together and get it across borders without the watchful eye of surveillance detecting it and being able to stop it.

Source is fairly linked to in the original article by the way...

Sanctions and terrorism: How the cartels use crypto to launder the proceeds of narcotics trafficking

Discover how drug cartels use cryptocurrency for laundering narcotics proceeds and how blockchain analytics can help combat these illicit activities.

Funny you should ask that.

Outrageous HSBC Settlement Proves the Drug War Is a Joke

If you're suspected of drug involvement, U.S. takes your house; HSBC admits to laundering cartel billions, loses five weeks' income and e...