Satan's sin "in the beginning" like Apostle John said, is the reason... for this present world of sin and death. There is no salvation in the flesh, as God ordained even Adam and Eve as being subject to death. And if that assignment to sin that Satan originally created had never happened then God's Plan of Salvation through His Son's coming in the flesh to die on the cross would never have happened.
Heb 2:14-15
14 Forasmuch then as the children are partakers of flesh and blood, He also Himself likewise took part of the same; that through death He might destroy him that had the power of death, that is, the devil;
15 And deliver them who through fear of death were all their lifetime subject to bondage.
KJV
1 John 3:8
8 He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that He might destroy the works of the devil.
KJV