^ That's really not how victory is defined. It differs from war to war. US objective initially was to destroy Al Qaeda, then it expanded onto taliban. If US fails in destroying Taliban, and Taliban are able to form a government in Afghan after US exit, then Taliban win. That's how their victory against soviets came. Winning a war has nothing to do with going out killing the enemy's leader or fighting like men. It's all about if you're able to make the enemy not achieve their objective. They can fight conventional or unconventional war, it's really irrelevant.
War has a strategic meaning, and here the strategic meaning is Taliban stopping US from achieving their objectives and forming a government. Showing up, killing US leader, etc is irrelevant. But yes, their true victory would only come if they are able to form a government.