chocandpatience – I have to preface my comments with the following: When anyone says that the gedolim “erred”, we are not talking about halacha. The possuk “lo sossur” deals with halachic items.In that context, a Possek is always right in what he says. When people question some ideas or decisions of Gedolim, it is in “milei de-alma”- matters that are not relevant halachically.
The words and opinions that came from gedolim before the Holocaust had nothing to do with halacha. It had to do with their impression of the world. In that, they erred in not recognizing the danger of Nazism.They are not nevi-im and no one puts blame on them- it is just that in their decision making, they were incorrect.
As far as your second question- the fact is that the Germans did not reach Palestine in the war and the people who emigrated before the war were saved.To say- as you imply- that the Germans could have been in Palestine and endangered the jews there is pure speculation.We can only deal with facts and the fact is that The germans did not reach Palestine.
Your last question deals with matters of deep spiritual significance- If, as we believe, HKBH directs the whole of the world, how could he have allowed gthe Holocaust? if you answer that there was a “hester ponim”, then you must also accept that the foundation of the medinah is also ‘min hashomaim”.
We cannot fathom HKBH’s intentions and all we can do is try to act as we understand and as we see in the world around us.