The Pakistani couple who took me in described Pakistan as being "wild", except in the cities and the larger towns, because there weren't enough police to constitute a proper "police service", and although there were enough soldiers, their officers were inevitably corrupt. It's not the case of "authority letting things happen", but a case of there not really being a national authority worth a fuck to be able to stop things happening in the first place.
It's easy for "terrorists" to set up shop in an environment where being policed is highly unlikely.