So the town is populated by deceased scientists. Fine. But then why is only Marie Curie there, and not also her husband, Pierre? If she has been "resurrected", surely he could have been too, right?
The main reason Mari can't get back to her own world is because the bridge between the island and the mainland broke down. Still, there are lots of occasions where it is shown she can travel across the water regardless, like when she goes on a boat trip, or even travels through space. What's going on?