Godzilla vs. Kong explains why Skull Island – the most unique place above ground – is populated by monsters. Similar to the world of dinosaurs presented in the Jurassic Park movies, Skull Island is home to not just Kong, but all sorts of monstrous, seemingly prehistoric creatures that can’t be found on any other ecosystem on the surface. The group that visited it in Kong: Skull Island came across several new species during their expedition, including Skullcrawlers, Leafwings, the Mire Squid, and of course, Titanus Kong.
For a while, it was perceived to be the most extraordinary location in the MonsterVerse, but that changed in Godzilla vs. Kong when Monarch and APEX’s team followed Kong into the vast Hollow Earth world beneath the surface and encountered even more fascinating creatures. There, they were attacked by the powerful, flying serpents known as the Warbats, and also spotted a Hollow Earth lizard, crab monsters, and more. The only place in the MonsterVerse that’s even comparable to what was found in the Hollow Earth is Skull Island.
As for why this small island in the South Pacific has such a special environment, it seems that Godzilla vs. Kong’s Ilene Andrews (Rebecca Hall) has the answer. According to Nathan (Alexander Skarsgård), Ilene had theorized prior to the film that “Skull Island was like Hollow Earth come to the surface”. It’s certainly true that Kong’s species and the Skullcrawlers are native to the Hollow Earth, but it would seem this statement holds true for everything else on the island. What further backs up this idea is the inclusion of the Leafwings in the Hollow Earth scenes. The monsters being a part of both ecosystems should erase any doubt about the link between the two.
Godzilla vs. Kong's novelization expands on Ilene’s theory. It was said in the book she thinks that various plants and animals from the Hollow Earth somehow expanded up from the tunnels and through the entry point, and then spread out across Skull Island. It’s likely the expansion was an evolutionary process that took centuries to occur. As for why it didn’t go beyond Kong’s home, Ilene believes this is due to the island being so isolated.
Unfortunately, the beautiful world spawned by the Hollow Earth is no more. All because of Ghidorah’s storm, the creatures and plants that once thrived on Skull Island are either dead or dying. But, Godzilla vs Kong indicates that many of the species found on the island may not be extinct. They didn’t find any more of Kong’s kind down there, but as noted above, they did see more of the Leafwings. And since all of the creatures from the island originated from the Hollow Earth, several of the same monsters and plants Kong thought were gone forever can be rediscovered in his new home.