> In fairness, there was no public evidence of the Nazi death camps up until they decided to turn the prison camps into that at the Wannsee Conference either.
> It was only in retrospect that we learned the true horror of the Holocaust.
If you think the Holocaust was just what happened in the gas chambers, I'm afraid you haven't learned the true horror of the Holocaust either.
Approximately 2.7 million Jews[0] were killed in the death camps as part of the so-called Final Solution between 1941 and 1945.
This was preceded by the so-called Euthanasia[1] campaign, which killed approximately 300,000 people deemed "life undignified for life" (mostly people with disabilities) - although the exact numbers weren't known to the public at the time, the program became so widely known following a proclamation against it by the Holy See (after Catholic authorities in Germany generally supported it) that there were actual protests agianst it in Germany.
The total number of people killed by the Nazis between 1933 and 1945 in what were later considered crimes against humanity - excluding those who died from conflict, disease, etc (i.e. from WW2 or its circumstances/effects) - is approximately 17 million[2] - more than six times the number of Jews killed in the death camps alone. Of those, 6 million were Jews: 2.7 million in the death camps, about half that many additionally included among the Soviet Citizens and POWs and another 2 million non-Soviet Jews killed outside the death camps.
Note that this number doesn't include civilian victims of the war - the Nazis specifically went out of their way to carry out mass executions in Poland and elsewhere. Many of these were carried out by the Reserve Police[3], often voluntarily with no threat or punishment for refusal other than mild disciplinary action (e.g. latrine duty) and social ostracization by their colleagues for "letting them down". Many more were carried out by the Wehrmacht on their way through the Soviet Union in case you're wondering how the myth of the "innocent German soldiers" is holding up to scrutiny.
> Complacency and a lack of accountability in the moment is how these things happen, and turn good people to sloth.
True, the full extent of the Nazi mass murders was hardly fully transparent at the time. But none of this happened out of the blue and there very much was a clear and obvious escalation visible to those who cared to see it - an escalation also easily predictable at several points throughout its course, by the way, except people (including foreign governments and foreign news organizations) very much did not want to acknowledge it for a number of reason from wanting to avoid being seen as alarmist or leftist to actively supporting parts of it and just hoping that the escalation will stop at the point where the outcomes are most personally beneficial to themselves.
The problem wasn't a lack of accountability. The problem was people rationalizing their own actions by wanting to be the good guy in their personal narrative. The Reserve Police didn't volunteer to execute civilians because of a lack of oversight, it did so because not doing so when asked seemed unconscionable when the alternative would have meant reevaluating all the horrors they had participated in up to that point.
We literally have testimonies of Reserve Police officers who participated in the killings saying they did nothing wrong and actually were the real victims for being put in such an uncomfortable position of having to carry out these killings - or in one case an officer stating that he had asked his colleagues to specifically let him kill the children as long as their mothers are killed first because then he could see it as an act of mercy to kill the orphaned children.
Hierarchical institutions are designed to create a culture of obedience. Obedience is how these things happen, not complacence or lack of accountability.
[0]: https://encyclopedia.ushmm.org/content/en/article/at-the-kil...
[1]: https://en.wikipedia.org/wiki/Aktion_T4
[2]: https://www.statista.com/statistics/1071011/holocaust-nazi-p...
[3]: https://en.wikipedia.org/wiki/Reserve_Police_Battalion_101