Why could they withdraw from Afghanistan? Al Qaeda has nothing to do with The Taliban. Bin Laden's Al Qaeda haven't made succeeded in a major attack against the US/Coalition for almost a decade. Their network has been massively disrupted, they have no money and little resources to plan an attack.
Can I have some of your opium please?
taliban let them stay in afghanistan... they shared the same training grounds and stuff...
al qaeda probably have loads of money from drugs you know afghanistan was full of poppy fields?