While some of the Death Eaters are definitely unpredictable (my own aunt is a shining example), their pushes into the rebel areas normally have a purpose. They either want to achieve something, punish the Resistance for something, or think it wise to invade a certain location for other strategic reasons. Attacking three different magical villages, even two in a single night, seems rather shambolic to me. Especially since the Dark Lord must have given his permission for this, otherwise it would never have happened.