Hey man, maybe you don't know how this thing works in Sweden but a lot of these Syria, Iraq, Iran and Somali gangs just want to emulate the US-gangsta scene ; they have their own hiphop, their own style that mimics the US. The younger guys rob, deal drugs, drink and the usual low-IA stuff while the older guys keep the business running by providing the needed muscle and their elders look away or sometimes they work hand-in-hand. They preach Islam because it suits their purposes and gives them the means to control their grip on the areas.
It's not a joke but it's an absurd mix of gangbanging and religion.