That's one of the many problems with cartels: they fight over control of valuable resources. Occasionally a single cartel gets a firm hold onto something and right about then, the US government swoops in to decapitate the leadership, re-initiating a war. I.e. What happened with CDS and CJNG after El Chapo's extradition to the US.
Also, if a certain skim percentage becomes acceptable loss to all parties, the cartels will want more.
Also, if a certain skim percentage becomes acceptable loss to all parties, the cartels will want more.