Perhaps the very job of being a policeman,obeying and enforcing rules you may not like,meant no big strain in obeying the Gestapo.
Also,remember,few were murdered in the home country,the Nazis sent them by rail to the camps.Thus the police didn't see the real violence and could pretend nothing unusual was happening.
Many Europeans also harbored suspicion and distrust ,even hatred, towards the peoples who were different ,i.e. Jewish ,gypsies, and mentally impaired;that made it much easier for the Nazis.
The Danes hid and protected their Jews and the Swedes gave passports and safe passage to thousands.The French collabration is one of the blackest smears on their national reputation.
There are books written, and courses given, usually titled “Methods of Control” or the like, and they are all about controlling, shaping population.
Police as individuals, formally, and their near trade school ‘education’ are horrifically ignorant of the history and politics of policing, and police by other names. Those that do by accident, time or otherwise become more catholic in their work, often become cynical.
NIxon,who I admired,gave us the EPA,whic is an ongoing disaster.
Bush gave us the declaration of our sworn enemies as a Religion OF Peace,and saddled the U.S. with the Department of Homeland Security.
It is obvious that most politicians care nothing for the restrictions of the Constitution.
Buchanan was probably the last U.S. President to be faithful to his oath.