You must be new to strategy, it is actually better for the winning side to keep the losing sides civilians alive. It is a waste of time and resources to kill that many people.
also, maybe you should look up some of these historical photos>>6995575
One of many guards and officials that received trials in the field >>6995563
Many Germans were forced to see the atrocities their people did behind fences by ally forces and were publicly shamed. Also, Germans themselves did not know many things that were going on. German families gave up their family members with mental disabilities to the state assuming they would be cared for, only for many of them to end being euthanized.
Not many went on trial, but soldiers who had to look at and pull the bodies of starved little girls from their shallow graves sure as hell made sure the people in town were not able to stay ignorant.