Because the Bible was written by some humans over the last millenia.
At the time, the complexities of ecology were not understood, or even properly studied, the enormous scale of the planet and the finite reaches of life were not fully discovered.
The Bible dictates the world is just a resource for man to exploit, so of course it doesn't mention that actually nature is a chaotic and violent struggle for survival for everything.
The Bible, God and Christianity all revere humans as the absolute apex of creation and entitlement. It's doesn't respect or recognise our humble origins co-evolving and struggling like the rest of nature. We are afterall, just animals ourselves.