Monarch: Legacy of Monsters reveals that Bill Randa is the first person to come up with the Hollow Earth theory, for which Dr. Houston Brooks is credited.
In Kong: Skull Island, Dr. Houston Brooks talks about a paper he wrote on the Hollow Earth theory.
It suggests that there are massive underground spaces isolated from the surface world. Bill Randa hired Brooks after reading this paper.
However, Monarch: Legacy of Monsters reveals that Bill Randa already had an idea about this world, as he had figured out a theory of his own with Keiko in 1955.
Bill Randa’s theory
In 1955, to save Monarch from shutting down, Shaw instructs Keiko and Billy to build a case for Monarch by drawing out a map and pointing out where the monsters can be.
Bill has long suspected that monsters such as Godzilla teleport to travel around the world. Hence, they are not seen often.
While studying his field notes again, he sees an ant going inside the hole that is on his map and coming out on the other side.
Bill Randa theorizes that the monsters live underground, and not just underground; what if there is another realm beneath the earth, inside of it?
Bill wonders if two different worlds are co-existing. This makes Bill the first person to suspect that there is another world beneath the Earth where monsters like Godzilla live.
Later in the MonsterVerse, the world beneath the Earth is called Hollow Earth.
Lee has been to the Hollow Earth
Lee Shaw confirms that he has been there before. Since parting ways with Cate, Kentaro, and May, Lee has been visiting all the Monarch outposts where these portals to Hollow Earth exist.
Lee firmly believes that Godzilla is not a mindless, destructive force. He knows what he is doing. He is keeping his kind in their world and humankind in theirs.
Lee has been purposefully destroying these portals, also called rifts, in an attempt to avoid another G-Day, the appearance of another monster like Godzilla that can destroy the human world.
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