If we go back to the beginning from the very first mortal kombat and the movie, mk was consisted of a tournament style version of taking over the world and the humans role was to save the world by stopping Shang Tsung from winning the 10th tournament. But near the end, liu kang faced off against shang tsung, and denied the evil from ever occurring.

So, now if we look at the situation in a different point of view, except on earth, where Liu Kang would have lost and Shang Tsung would have confirmed his 10th victory, the whole world would be corrupt. All in evil hands, everything dark and terrifying. In the movie signs were shown where the golden gate bridge and the world's popular sites were taken over. If the world was to be taken over by the evil of the dark sorcerer, could the humans survive and be given a chance to make a tournament of their own in order to reclaim the earth? After the 10th victory in a row by humans, could earth be given their right back? I don't think so, if the world is evil, everything is evil, and if the world is good, you'd have to do so with your word. the world is a corrupted place with laws that go against laws, and making some laws unfair and unjust, but for the sake of humans, some laws just don't even get the chance to look at.
If the world was full of evil, the world would be even filled with much more evil with alliances and deceptions and all amongst themselves, maybe the humans could manage to survive in the doom of mankind at the very deep pits in cellars constructed by evil hoping that someday the evil would slip a foot and crash each others' cars into one another.
What else do you think could happen?