Final answer:
Cartels typically cease to be effective due to enforcement efforts by governments, internal competition and difficulties in maintaining secrecy and loyalty within the organization, and external competition. The high stakes of the illegal drug trade and pervasive corruption make cartel longevity particularly challenging, especially in the context of Mexico's war on drug cartels.
Step-by-step explanation:
Most cartels cease to be effective because they face substantial challenges, such as enforcement actions by government authorities, difficulties in maintaining collusion among cartel members, and competition from within and outside the cartel.
The enormous profits from the illegal drug trade drive the formation of cartels, but these same profits also fuel intense competition for control, which can lead to the cartel's downfall. Government efforts to combat drug cartels, especially through agencies like the DEA in the United States and militarized operations in Mexico, have focused on disrupting these organizations. The Mexican drug cartels, in particular, have struggled with the Mexican government's war on drugs since 2006.
Internal enforcement is complicated by the difficulty of finding hard evidence of collusion since cartel agreements are formal and provide actual proof of their actions. Due to this, in countries like the United States, most collusion is tacit rather than based on formal agreements.
The situation is further exacerbated by the cartels' tendency to corrupt local law enforcement and government officials, making enforcement even more challenging. The scale of corruption and violence related to the drug trade is significant, with homicides and the integration of drug money into local economies being notable problems facing Mexico.