TL;DR: The Taliban has lasted for so long because it has a durable organizational structure and safe haven in Pakistan. Undercutting the Taliban is more complicated than rooting out its network of poppy cultivation. Yes, the sudden removal of its drug funds would likely hurt the group, but the organizational structures, recruitment networks, and other streams of revenue will endure. The Taliban will continue to hide out in ungoverned spaces (made worse by the withdrawal of U.S. troops) or civilian populations to evade counterinsurgency efforts.
Longer answer:
To answer this question, it is important to understand why the Taliban was formed and how it has developed over time. The group has used revenue from opium to fund its activities, but its operations and goals have never been solely about drug cultivation and production.
The Taliban was not created as an organization to make money. It was formed in 1994 by a cadre of religious scholars that sought to establish an Islamic government in Afghanistan. At that time, Afghanistan was engulfed in a power struggle between competing warlords. The Soviet Union had withdrawn from Afghanistan in 1989, leaving a puppet government behind to manage the country. In 1992, the USSR-imposed leader resigned, and several mujahideen factions attempted to build a coalition interim government. However, this cooperation soon stalled, and the factions began to fight for control of the country rather than share it. This violence began the Afghan civil war.
The Taliban emerged during this conflict. Composed of religious scholars and students dedicated to a strict interpretation of Islam, the Taliban sought to take over the country and impose an Islamic system of governance. The group's original motives were not driven by the desire to make money, as might be expected in a drug trafficking or criminal organization. Rather, the Taliban is better classified as a center-seeking militant group (i.e., an organization that uses violence to to overthrow and replace the government).
This difference in goals between the Taliban and more traditional criminal organizations is important to note. Given that Taliban militants are fighting for more than just money, undermining the drug trade in Afghanistan is not enough to stop the Taliban from engaging in violence. It may impede the group's ability to pay for operations, but it will not address the underlying motives that drive Taliban militants to carry out attacks in the first place.
The Taliban quickly routed other armed factions fighting in the civil war and took control of Kabul in 1996. (For a great explanation of how the Taliban did this, see Organizations at War in Afghanistan and Beyond by Abdulkader Sinno). The group then transitioned to become the government of Afghanistan, known as the Islamic Emirate of Afghanistan. Though it was only recognized by a handful of countries, the Taliban government effectively controlled more than 90% of the country (see Sinno 2008, 222 for more info). Also see here for more on the Taliban's goals and organizational development.
During this time, the Taliban was not dedicated to drug cultivation. Rather, Taliban leader Mullah Mohammed Omar actually took several measures to cease the production of opium in Afghanistan. Between 1997 and 2001, the Taliban issued multiple bans on poppy cultivation. The group claimed to have implemented the bans for religious reasons and lost money from the policy because it could no longer collect taxes on opium production.
The Taliban ruled Afghanistan until the United States and its allies invaded in 2001. The Taliban government in Kabul quickly fell, and most of the Taliban leadership fled to Pakistan. Now much weaker, the Taliban turned to insurgency tactics to fight for control of Afghanistan. The group cultivated local ties and blended in to the civilian population so that its militants were difficult for U.S. forces to identify. Over the last two decades, the group has slowly regained control of territory in Afghanistan, benefitting from the weak Afghan security forces and the U.S.'s under-developed plan to establish a new government in Afghanistan.
Yes, the Taliban has relied heavily on drug cultivation to fund its activities during this insurgency. However, its organizational network has become so well developed and protected in Pakistan that it has been difficult for U.S. or other forces to 'disrupt' it, as you put it in your question. Pakistan has effectively protected the Taliban from counterinsurgency operations in its territory, providing the group with a valuable safe haven. (For Pakistan's motivations, see this article.)
Moreover, the idea of neutralizing the Taliban by killing or capturing its leader (as in the El Chapo case) is not guaranteed to be successful. There is a large literature in political science on the effectiveness of 'leadership decapitation' in armed groups. Since leadership decapitation is not randomly assigned among groups, it is incredibly difficult to estimate its causal effect. Some studies have found that decapitation is associated with group decline (e.g., Price 2012), while others find no effect (e.g., Jordan 2009). It is clear, however, that for groups with safe havens or a long history of successful operation, it is very difficult to dismantle the entrenched organizational structures, finance streams, and recruitment networks that keep militant groups going.
In sum, the Taliban is a highly developed, flexible, and durable organization. It has gone from fledgling armed group to government of Afghanistan to highly effective insurgency over the past 30 years. Since 2001, the Taliban has benefited from a safe haven in Pakistan, which protects it from U.S. and Afghan counterinsurgency efforts that seek to dismantle the group. The current withdrawal of U.S. troops from Afghanistan is creating a power vacuum in which the group can regain control over large swaths of Afghan territory.
Undercutting the Taliban is more complicated than rooting out its network of drug cultivation. Yes, the sudden removal of its drug funds would likely hurt the group, but its decades-old organizational structures, recruitment practices, and alternative streams of revenue will endure. The group will continue to hide out in ungoverned spaces or civilian populations to evade counterinsurgency efforts.
