When Adam and Eve ate of the fruit, they began to die. They had sinned, and needed restoration...

But something that is being missed in this conversation is the other party involved: the snake, or rather Satan. Satan had begun his work to counter God and to continue his effort to become all powerful (the reason he was thrown out of heaven in the first place.)

Now that Satan had enticed them, and they were no longer sinless and perfect; the plan was prepared... not just for the redemption of Mankind, but for the crushing of the serpent by the Son of God. This is a war of good and evil... only by Christ dying, conquering death and hell, and rising again could everyone know ...including Satan... that GOD is the Almighty One.