The idea that anarchism leaves a vacuum or creates disorder is a misunderstanding of what anarchism really is. It's not simply the absence of a state, but it includes the deliberate construction of horizontal structures and institutions that effectively leave no room or reason for a state to exist any longer.
Anarchism does not reject organization, in fact the "circle" in the famous circle-A is actually an O that stands for Order.
The anarchists are providing tangible services, bombings and bank robberies are not the only actions they take. Squatted buildings become neighborhood social centers, shuttered factories have been seized and spun back up into production, consumer goods have been expropriated and distributed for free, and fascist attacks on immigrant neighborhoods have been repelled. As the article says, the perception is that anarchists are the only people who can do some of these things, due to the inability or complicity of the state's forces.