Because evil has to exist. Recall where I said He cannot empower you with understanding? Evil had to exist, and it came from free will. Had we not this understanding of the concept of evil, we might have committed evil after He made us gods as well, which is obviously a giant problem. Who knew Stan Lee was such a theologian? "With great power, comes great responsibility." This life is basically a giant background check before we become gods, that if we pass, we understand evil and will not commit it.