[ijriims]

Of course, the disaster was not a nuke, so the effect should not destory Kuwadorian in any case.

But we should not jump to the conclusion that the gold was in Kuwadorian or Eva hid in Kuwadorian actually.

My guess was there was extensive underground tunnel system and the location of the 10t gold was hidden well within the maze. Kuwadorian was just another route of the tunnel system. If we believe Eva did solve the epigraph in EP3, then she shoud only know about the route to gold but not Kwadorian.

Actually, it was unlikely for the gold to be in Kwadorian. It was initially a residence for cliff-falling Beatrice. And there must be someone (at least one female, in this case Kumasawa) other than Kinzo to take care of her when she was still a child. If the gold located within the Kwadorian, then it would be too risky concerning Kumasawa's nature...

The reason for Kumasawa's temporary leaving should be that she tried to find the gold hidden in the tunnel system but lost, then Kinzo found out and fired her. She latter pleaded to him and successfully came back to the family. (also the reason she was never given the right to bear the one-wing eagle symbol as she was proven untrustworthy.)