You are purposely referring to those Rabbanim who advised not to leave and to those laymen who said to leave. This is not a fair argument. If a Rav said Europe is about to explode and someone else said that it won’t, then who should they listen to?
There is a person for every view. Finding the one, after the fact, that turned out to be the case doesn’t show anything. If I run down every street yelling, “Your pot is bubbling!” and eventually it turned out true for someone, that proves nothing at all. On the flip side, when a sudden current swept away a professional swimmer that doesn’t put a shaddow on his professionalism.
People were not wholesale advised not to run. And if you are comparing, as many do, before anything started when Rabbonim kept people from going to places where they will lose Yiddishkeit while others urged people to go — not out of any long term understanding, but out of ideology — then you are comparing apples and pebbles.
You are actually picking on exception rather than the rule. Besides, in Poland nobody told anyone not to worry, so why didn’t they run? This is why I mention the Navi. It doesn’t help.
These points were raised earlier in the discussion.