I think you are giving them far too much credit. It's more likely their absence made the decision to go all-out easier too condone; rather than be predicated on the fact via some grand conspiracy to evacuate jews years ahead of time. They were allowed to leave under those conditions because Hitler was going the route of expulsion through amicable means. Seems to me, he was more interested in showing the world, through example, what it meant to be free of the parasite. That it also didn't require bloodshed too do it. Not because some kike 4-D-chess move.