according to a friend of mine who spent several months as a prisoner in Buchenwald* was that these camps didn't happen by accident nor were they simply thrown together. They were carefully designed by engineers, architects, and other educated people. For example, the crematoria at places like Auschwitz had to be specially engineered to handle thousands of bodies per day. It's easy to dismiss the Nazis as brutal, sadistic thugs (and most of them were), but many of them and the people who enabled them were from the the ranks of professionals. It's easy and proper to blame the Nazi leadership and the brutal guards, but it's just as necessary to blame those who made the camps possible.

*As Jim pointed out, as horrible as Buchenwald was, it was vastly better than Auschwitz. In a way, it's almost obscene to compare the degrees of horror at the different camps, but there was a substancial difference. Buchenwald was a concentration camp where thousands of prisoners were kept in horrible conditions, fed a diet that guaranteed slow starvation, and basically worked to death at slave labor. Auschwitz was a death camp. It had all of the horrors of the concentration camps along with assembly line mass murder.