Their governments have deliberately imported lazy, aggressive, military-age males and given them a status they could never have achieved in their home countries: free food, free clothing, free lodging, free medical care, no requirements to assimilate, literally everything they need. Their imams tell them they're a conquering force and there's really no good reason for them not to believe that. Meanwhile veterans are being moved from what lodgings they might have managed in order to accommodate the invaders.
And the government of the United States is doing exactly the same thing.