Indeed they were. But at the time of the trials there were a best estimate; nobody will ever know for certain EXACTLY how many were killed. Other evidence and documents did not emerge until after the trials. Some of the Einsatzgruppen records and some of the death camp records were destroyed...
The Nazis used the "Mischling Test". If you had one Jewish grandparent you were a second degree Mischling (two and you were a first degree MIshling). If you had one Jewish grandparent you were classified as "non-Aryan" and had some restrictions imposed.
The Nazi race laws were quite complex...
Is it the education system though? I was educated 60s / 70s and WW2 / the Holocaust was never covered. However, I was aware of the holocaust from a fairly early age. Whether that was because my father and his brothers all served in WW2 I really don't know. So I can't recall how I knew, I...