For one last time. An application for an order of mandamus is not a lawsuit or sign of ungratefulness, anyone dealing with the German state can make use of it and it's been done so on daily basis. The article is misleading in that it depicts refugees as people suing the German state in fact it's German officials or lawyers acting on behalf of refugees.
ISIS is not just soldiers, same as the 3rd Reich wasn't just the Wehrmacht. It takes an entire apparatus to run a state and even if we do not recognize ISIS as a state it does have a sufficient apparatus run its empire by rules, rules which are actually not the ones made by its soldiers but by its own set of high-ranked officials (clergy, policemen, urban militias etc.). Yes, you can run from that. People have been running from dictatorships and tyrants since millennia.
In your medieval view people fight for honour and land, and some set of traditional goals, the reality is that might have been true for some in the beginning but at this stage of the war the only reason to fight is influence and power. Both being somewhat out of reach goals for the common man as they are high up on extremist agenda.
Also a lot Syrians who have actually fled here do want to get back. They are thankful if they are actually accepted here but they don't want to stay here forever. Frankly it would be a surprise otherwise since a lot of have family ties, businesses and homes.
I saw a documentation recently where Merkel's motives were a topic as well, former
Democratic Awakening member Rainer Eppelmann and one who knew her since the beginning surmised that it's Christian motives.