I don't think this is true at all. There is a tendency amongst westerners to assume that the official government is inherently legitimate. But legitimacy is ear

I don't think this is true at all. There is a tendency amongst westerners to assume that the official government is inherently legitimate. But legitimacy is earned, not granted by the 101st Airborne Division. You are the legitimate government of an area if you have an effective monopoly on the use of force in the area, if you provide vital social services, if you perform dispute resolution, etc. In significant parts of Afghanistan, the Taliban are seen as the legitimate government while the children from Kabul are seen as inept crooks. In those areas, random violence undermines the Taliban's goals: once you've convinced people that you're the legitimate governing authority, you have to keep them satisfied, and random violence makes constituents very unhappy. The same confusion often erupts when people consider southern Lebanon.