We are not mortal because we sin; we sin because we are mortal. St. Paul did not say that death is the sting of sin, but that sin is the sting of death (1 Corinthians 15:56). It is not the sting that causes the bee but the bee that causes the sting.
For the perishable must clothe itself with the imperishable, and the mortal with immortality. When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true: “Death has been swallowed up in victory.” “Where, O death, is your victory? Where, O death, is your sting?”The sting of death is sin, and the power of sin is the law. (1 Corinthians 15:52-56)
Since the children have flesh and blood, he too shared in their humanity so that by his death he might break the power of him who holds the power of death — that is, the devil — and free those who all their lives were held in slavery by their fear of death. (Hebrews 2:14-15)
The power of death has been broken, so also the power of the devil, who held the power of death — and with that, the power of sin.