Dug this one out again for another look see. I noted that there appears to be something akin the common representation of super computers in the movies, mostly mysterious blue lights. Behind the big throne in the Hollow Earth is a hexagonal structure with lines of blue lights going up it. There are smaller columns around the throne, and each is hexagonal. This suggests a higher intelligence created the kaiju, at least the ones in Hollow Earth. Maybe nonterrestrial intelligences or Pelucidarian intelligence?
Caveat: This may be a cinematic dead end, an idea that was worked into G.v. K. that will never be followed through in later movies. I think it would be fun to follow this path.
Caveat: This may be a cinematic dead end, an idea that was worked into G.v. K. that will never be followed through in later movies. I think it would be fun to follow this path.