Your numbers need some illuminating:
The Taliban have somewhere from 50,000 to 60,000 "core" fighters. But there are also anywhere from 80,000 to 160,000 militia style combatants with aligned groups.
The Taliban is sort of a franchise operation - you bring some men along and they will help arm them and set them up to control a territory. The territory is then "yours", but the Taliban get to control it. EDIT: These are 'holding troops' - the can occupy ground, but can't really conquer new territory.
There are also many as half a million "armed sympathizers" from tribal groups both within Afghanistan and in some of the surrounding regions (mostly across the Pakistan and Turkmenistan borders, also in Iran). These guys will basically help the Taliban assert control, even if they're not Taliban themselves.