So, those from that world all employed their unique methods and experiences to manage some stores, and these stores seemed to do very well as you've described, allowing them to gain more potential, and indeed making their lives here much more comfortable.
At the time of the Yellowing, although this world had already become aware of the existence of another world in a parallel space, and it was very likely that world was quite similar to their own, for them at that time, finding this hypothetical pathway might have been a very bad thing. They couldn't guarantee that the people from the other world would have no desire to rule their world.
