We can't imagine the horrors going on beneath our feet in deep underground hell-holes. When God created the earth, He carefully prepared all we needed to sustain ourselves. Then he created "man" - Genesis 1:
“So God created man in His own image, in the image of God He created him; male and female He created them. God blessed them; and said to them, “Be fruitful and multiply, and fill the earth, and subdue it; rule over the fish of the sea and the birds of the sky and over every living thing. I have given you every plant yielding seed that is on the surface of all the earth, and every tree which has fruit yielding seed; it shall be food for you."
When Satan and his fallen angels were cast out from heaven to the earth, Satan immediately set out to destroy every single human soul on this earth. He has been hard at it for thousands of years. Sadly, we humans have made it way to easy for his deception(s) to work. We are the last hope for humankind to survive and by God we will.