The majority of Arabs (Algerians, Moroccans, Malians, etc.) came to France as soldiers and laborers at a time when their countries of origins were still French colonies. They therefore were French citizens. Some more were "invited" to come afterwards since France lacked labourers in some industrial and agricultural sectors.
Those integrated quite well, but the situation started to desagregate in the 60's, together with work and housing situation, when the first generation labourers brought their families in. The present situation has to do with the lack (real and supposed) of integration prospects of the second and third generations, the continued unemployment, housing problems, discrimination, and the lack of a decent integration policy.
Of course, the relatively recent arrival of islamic rabble rousers has helped nothing ...