It's a proxy war like many of the proxy wars happening in these contention points. War is expensive and destructive. Which means you'll have difficulty collecti

It's a proxy war like many of the proxy wars happening in these contention points. War is expensive and destructive. Which means you'll have difficulty collecting any revenue and you'll need a constant stream of money to finance your soldiers. Don't be deluded but most of these militia are working for money, not for "god". In the case of Afghanistan, you got yourself with Iran, Russia, China, Pakistan, and the US (and its allies). Afghanistan is a great place to yield control over the region. So it was a war of attrition. Of course, the biggest losers were the Afghan themselves but they had little say in this conflict. Now that the US left, there is a tab to pay to the Taliban. That, or they'll look for a new sponsor. Leaving at this point (where Taliban are quite powerful) is not that stupid (might actually be smart). Pakistan and Iran (and maybe China?) have created a monster that is quite hard to control than a traditional army. Now, they are all living near this monster.