A 3 or 6 months probatory jail would have been possible and in lines of what he would have get if he were a French citizen. On the other hand French justice system is pretty much saturated (especially in Marseille with the recent bursts of drug affairs) and tend to punish more violence in...
Unless the Frech law has changed, the maximum football ban you can be sentenced is three years in France.
So no, the sentence is not extremely lenient. He could have been sentenced to jail or probatory jail but that would have been on the harsh side.