The move towards owning their own businesses among the Turkish population in Germany took place around the early 80's. 2. As the Turks are the largest minority in Germany, it was just a question of time. In France, food from Northern Africa is available all over the country. Go for them, incredibly good. Kebabs are sort of balanced, not only meat but fresh vegetables as well.
Kebabs are cheap.
Germans have this tradition of bratwurst shacks at every corner. So the kebab shops represent some continuity of this tradition. McDonald's is a rather new concept and there were times when they had a really bad image, their beef being responsible for the destruction of the rain forest by hordes of cows. Not to mention that a lot of people thought that the nutritional value of a Big Mac was somewhere close too zero. They are filling.