Mass Murders and concentration camps are nothing new in the human condition. The existed long before 1930. And they will exist for ages after us. They are horrifying every time, every place.
The difference was the location and the industrialization of it. We also know that it’s going on. We choose to ignore it as a species.
Also, the Germans had the audacity to document it, and film it.
The Soviets didn’t film the Gulags.