I’m not sure I agree with “downfall”, since you and I are living examples of the direction Adam took in the Garden. Isn’t everything that has happened to man since the Garden leading us to the need for a Savior to rescue us from a situation that we ourselves have no power to overcome? There is but one name given under Heaven whereby man might be saved. Acts 4:12 from memory, and poor memory.
Why did Adam sin? Why do you and I sin? Eve sinned because she wanted to be like God. However, Adam did not want to be like God; he wanted Eve, worshiping the creation instead of the creator and not seeing God great as He is. Adam did not go to God with his problem so that God could solve his problem. I believe God would have caused history to be completely different if Adam would have gone to God for help instead of seeing things as hopeless and gave into sin.
You claim to be a Mormon. As such your religion says no one enters Heaven except they are approved by Joe Smith. Didn’t you know?