The government the U.S. has been building for the past 20 years at the cost of 3,500+ American lives and over $2.5 trillion? It collapsed in 4 days.
What a waste.
Afghanistan became a "forever war" because there wasn't a good time to pull out. There never is.
As far as I can tell what became the primary purpose of the mission in Afghanistan was to make the Military Industrial Complex a lot of money. From that standpoint the mission was an incredible success.