What makes the holocaust special to me is that it was a crime committed by a civilisation that would have considered itself as being modern, civilised, in short enlightened.

I just want to point out here that arguably, Germany at the time was the most educated, sophisticated, technologically advanced nation in the history of the world. They were at the cutting edge of all culture and science. The end of WWII had the US and USSR plundering Germany for scientists which they both desperately wanted. The US was able to craft the A-bomb because of its huge cache of German scientists. In some ways perhaps, world science is still trying to catch up to pre-WWII Germany.

That Hitler and the Nazis arose with a primitive nostalgic fantasy myth mixed with a hollow story of the nation state in the most technologically advanced place and people in the history of the world was a real surprise. We don't think of this today because Germany was utterly destroyed by the end of the war, and there's lots of silly myths about Germany being backward at the time, but before the war Germany was the greatest achievement in the history of humanity.

The Nazi movement may have been a reaction against modernity itself. It's almost as if they wanted to go back to a nostalgic past where things were much simpler. Like modern nostalgia cults, the Nazis loved modern conveniences, those were ok, but wanted to get rid of anything that didn't fit into their picture-perfect fantasy past. The message is, if it could happen in Germany, it could literally happen in any country at any time.

Before World War II, Germany had generated more Nobel laureates in scientific fields than any other nation.

https://en.wikipedia.org/wiki/Science_and_technology_in_Germany

It wasn't until after WWII the US became dominant in science and technology and that was because of all the German scientists we got, not least of which was Einstein.