The answer is very simple. Germany has become the vassal state of Turkey
A million Turkish live in Germany, and the Turkish dictator keeps a large part of them under his control. They have to serve the Turkish army for example.
First of all, more than a million Turkish live in Germany, somewhere on the order of 1.5 Million.
Second, not all of them have to serve the Turkish army, even though I'm unsure how many would be legally required to do so.
Third, somewhere on the order of another 1.5 Million Germans live in Germany which have Turkish ancestors.
Fourth, just to put that into perspective, somewhere on the order of 1.5 Million people with Polish ancestry live in Germany, as well as half a million Italians*, half a million Romanians*, some couple hundred thousand Russians*, Croatians*, Greek*, Bulgarians*, Serbs*, Syrians*, French*, Spanish* etc., etc.. You name it, we have it.
Even our Secretary of the Interior has obvious French ancestry.
Germany is a multi-ethnic country, just like most in Europe and there's nothing special about some of the inhabitants being legally required by their respective "home countries" to do their civil duties in exchange for e.g. voting rights there.
* always + offspring