One of the greatest failures of both past and current administrations. The reason a majority of Nazis weren't put on trial was simply: If they had, every single structure would have fallen apart, because they were in every level of administration, etc. There simply - from the perspective of the allies - weren't any people that could replace these structures adequately. So they didn't pursue. Same with the 2008 financial crisis. A single banker got charged. Why? Because they would have had to fully dismantle every established system to really root out the people responsible, because they're so interconnected. Stabilizing the shit ass system was a priority over seeking justice.
It always will be, if the infestation just spreads far and deep enough. Which is becoming a real concern again.