That just seems so fantastically unlikely that I wonder if any of the other books in that setting explain it.
Not in any depth/at all and it is the fantastically unlikely nature of it that is one of the attractions of the series. As the setting is possibly an infinite plane, one of many, it helps get you straight into the idea that this is a strange and almost dream-like place. After all it has to be pretty odd to spawn it's only literary genre, even if very little has been able to achieve similar heights of weirdness.