All the genocide in the Nazi timeline would certainly create a lot of vacancies the victims' alternates could use to flee from whatever was happening in their world. I'm guessing they were refugees since they looked like a random group of civilians including children. If I was stepping into an alternate Earth I'd certainly want to allay the concerns of whoever was there by explaining who we were and why we were coming through. That way they wouldn't consider us a hostile incursion. If there was going to be another season then okay, to be continued. Under the circumstances though ... why foreshadow this event from the season's first episode, then not give us so much as a hint?
It's interesting that they happened to arrive mere minutes after the facility changed hands, and it was safe for them to do so. You wonder how they knew.