They absolutely are. Each cartel is a group of various drug lords all operating together to keep the price of their product high, and enforce that through violence.
The Sinaloa cartel for example is one organization of drug lords colluding and operating together across numerous nations and territories. It was originally an agreement between El Chapo and Izmael Zambada Garcia to work together trafficking drugs instead of competing because it meant more profit for both of them.
Combined, correct they are not one cartel. That’s why it says cartels and not “the cartel”.