The apostle Paul is saying that because of Adam's sin, all of mankind is now sentenced to death and eternal condemenation because of one offense. It is the condition of mankind and there is nothing we can do about it. We are born spirtually dead and without hope and a sinner by nature.
BUT because of the second Adam which is the Lord Jesus Christ and HIS righteousness all those who have faith are now no longer under that sentence but God imputes the Lord's righteousness unto us and we are justified by His Grace and mercy this is the result of one man's obedience. (justified - just as if I had never sinned)
The verse isn't talking just about death physically but the condition and eternal condmenation that we are all under just by being a human being.
consider this"
But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. Genesis 2:17
Well Adam and Eve didn't die physically that day according to the scripture but they did die spirtually. The Lord kicked them out of the garden. And this judgment was passed onto every person born into this world because of ONE man's offense
So, If one man's sin caused this horrible condition... consider what one man's righteousness did for mankind.
Romans 5:18 So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men.
Jesus obedience resulted in LIFE to all men. But men still die physically.
Elijah and Enoch's faith was counted to them as righteousness. God was always looking to the cross and what the Lord Jesus Christ would do. This is why the blood of animals only covered their sins under the law... it was a type of the Lord. But only the Lord washed them.
If someone has more insight in this please feel free to correct me but I believe that is what the Apostle Paul is saying when you put all of it into context.