What was it about the Holocaust that kept so many witnesses quiet?

Answer 1

The same or similar factors that are now keeping people quiet about war crimes and mass murder by Zionist Jews and their supporters, and there's a lot less excuse for it, too, now because we are living in a world where a vast section of the population has access to information. This wasn't so much the case before.

Answer 2

I hear that things happened there that were too gruesome to mention.