Sure, a Bin Laden hunt was necessary but all the rest?
Indeed. It was never really evident back then what the end-game would be. As with Iraq, it was a case of install a puppet government, rebuild some stuff we broke, train some of their guys to be policemen and soldiers, then beat a hasty retreat for the exit, declaring "job done".
We could have saved ourselves a whole heap of heartache and treasure if we stuck to the original model of using SF teams on the ground and B52s in racetracks overhead.