Also worth to note that most of killing in concentration camps started in 1941 (https://en.wikipedia.org/wiki/Final_Solution) and even then it was hard to prove it because were no cameras everywhere like today, so it was word against word.
And most people tend to not believe scenarios that they are afraid of.
RandomMe44 t1_j6nw591 wrote
Reply to comment by LebSonny in ELI5: How did Elie Wiesel and fellow Jews not know about the concentration camps/Nazi exterminations? by LebSonny
Also worth to note that most of killing in concentration camps started in 1941 (https://en.wikipedia.org/wiki/Final_Solution) and even then it was hard to prove it because were no cameras everywhere like today, so it was word against word.
And most people tend to not believe scenarios that they are afraid of.