The Holocaust was simply the European propensity for mass killing intersecting with novel technologies like the computer, the internal combustion engine, and novel developments in chemistry. What the English did with famine and the Belgians did with machetes, the Germans did with gas. Colonial nations had engaged in the targetted killing of vast numbers of people before then and achieved mass murder with great efficiency. The Germans simply brought these processes back to the European continent and combined them with the latest developments in technology.