So, as you say above, "Before salvation can be ours it was necessary for Jesus to defeat sin, death and the devil."
Now, I understand why this doctrine is a delusion because, sin has become more frequent after Jesus' death than before he was born which has become an evidence that Jesus did not defeat sin.
More people have died after Jesus death than before he was born. It means that Jesus did not defeat death.
The devil has been spoken of much more since Jesus died than before he was born which means that Jesus did not defeat the devil.
Can any one find any sense for this Christian doctrine? I don't think any one can because the Prophets of the Lord said that no one can die for the sins of another. (Jer. 31:30; Ezek. 18:20)
The New Testament is a spiritual book written by Christians for Christians.
Since you are not a Christian it is not for you, 1 Corinthians 2:14.
Maybe you should try reading comic books or something.