This comment presumes a modern understanding of citizenship. Jews living in Germany were seen as Jews, not Germans (just as Jews in Russia were not seen as Russians). This humorous quote by Einstein is based on this notion: https://www.goodreads.com/quotes/93643-if-my-theory-of-relat...
I admit I used the word "citizenship" in an inaccurate manner. Please allow me to clarify and correct myself.
In terms of technical, legal citizenship, that (presumably) became available to Jews in Germany upon their emancipation in 1871. This opportunity was revoked a mere 64 years later in 1935 with the introduction of the Nuremberg Laws. Citizenship in this sense is a modern invention.
What I meant above was citizenship in the sense of belonging to a particular group. A person could be a German in a legal or social sense, and I meant it in a social sense. The Jews were never seen as being "authentically" German. They were seen as a foreign people living on German land. This certainly contributed to the ease at which their legal status was stripped.
Thus, not a single Jew who was a German (in either sense) was murdered in the Holocaust, since that is an empty category.
By the way, this attitude wasn't particular to Germany, but all over Europe, from Russia to France.
