They've been doing a lot of governing! Collecting taxes, providing schooling, and brutally enforcing the (sharia) law. They've even assembled a military to protect their growing interests. It really resembles a younger US (from their revolutionary days).
A good size chunk of their people/leadership is from Saddam's original regime. If they're acting any worse than they have previously it's probably because they're stuck engaging in asymmetric warfare against the western powers that removed them from play for absolutely no reason whatsoever. The British very much viewed the US revolutionary groups as terrorists as well because they weren't lining up and exchanging gunfire in open fields as was the norm. They hid in the bushes like guerrilla fighters and brutally assassinated honorable soldiers.