Why did death reign from Adam to Moses even over people who did not sin like Adam?
Death reigned from Adam to Moses because Adam's one transgression brought sin into the world, and death came with sin and passed upon all men, for all have sinned. Even those who did not sin by a forbidden-fruit transgression still died, since the law had not yet been given and sin was not imputed; Adam is a type of Christ.
Les explains that the need for justification by faith began in the Garden when Adam fell, and death came with sin. Paul concludes that by one man, Adam, sin entered the world, and death came with sin, so death passed upon all men, for all have sinned. Until the law, sin was in the world, but sin is not imputed when there is no law. Nevertheless, death reigned as a king from Adam to Moses at the giving of the law, even over those who had not sinned after the similitude of Adam's transgression—that is, they were not faced with a tree and a forbidden fruit. So death's reign was not limited to those who repeated Adam's exact act. Les further notes that Adam is the figure, type, or picture of Him who was to come; Adam is the first man, and Christ is the second man, or second Adam. The human race is therefore in a dilemma: we are not only sinners but also under death. Spiritual death has already taken place—we are born dead—and physically every human being will approach death someday.
Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam’s transgression, who is the figure of him that was to come.