Someone taking over Afghanistan is what led to the problem in the first place. We helped them rebel against Russia then walked away, leaving them in chaos for a decade, until finally the Taliban took over and made it a terrorist safe haven. Nation building serves a purpose, helps turn an enemy into an ally. Look at the difference between the ends of WWI and WWII.
Right. We helped the Muslims chase the Soviets out of Afghanistan. Then the Muslims based in Afghanistan attack New York city. Are you incapable of learning anything. Let your enemy spend resources dealing with lunatics.