Satan is the ruler of this world, as referenced in the Scripture verses below. Adam and Eve and indeed, by default, all of us, were the intended rulers of the world. When Adam and Eve sinned, they handed over the keys, as it were, to the world, thereby placing control and rulership in the hands of satan (Unless his name appears at the beginning of a sentence, we will not dignify the name of satan by capitalizing it).
John 12:31 New King James Version. “Now is the judgment of this world; now the ruler of this world will be cast out.”
John 14:30 New King James Version “I will no longer talk much with you, for the ruler of this world is coming, and he has nothing in Me.”
John 16:11 New King James Version “… because the ruler of this world is judged.”