Many people these days believe that Kaiju's don't exist in real life, and only in movies and fiction of other media as revealed on television by younger people. What they didn't realize is whenever someone passes from this world, they end up where these beasts are actually real, and inhabit an island with no humans at all.
Dozen's of people don't know which kaiju they would end up becoming, because of the possibility of being bigger than what they were millions of years ago, and come in different forms. Another thing was, some kaiju's were actually half human, but the half-humans were the same size as the kaiju's as they developed the same power as them, and were strong enough to survive both volcano eruptions, meteor showers, and nuclear explosions that are capable of stopping nuclear wars.