Jesus replied, “I tell you the truth, everyone who sins is a slave to sin. (John 8:34, 1984 NIV)
God gave authority over the earth (IMO the physical realm) to mankind. Then when Adam sinned, he gave himself and everything under his authority to Satan. This does not mean God lost his overarching authority over everything (Psalms 24:1-2). (He remained The Creator.) It means men acquired a spiritual nature descended from Satan—and they also reinforced their submission to Satan whenever they sinned.
When Jesus paid for the sin of the world, the sin which separated people and creation from God died with Jesus and authority over mankind and the world went to the Redeemer, Jesus.
Even though everyone's sins have been paid for, people are not forgiven of their sins unless they genuinely seek forgiveness (2 Corinthians 7:10a and others), otherwise they continue to affirm that they want someone/something to be their master other than God (who is our morality). Repenting and accepting God as one's God means yielding to and accepting his Lordship. When someone does this, God grants the truly priceless gift of rebirth in Christ (since they were dead to God). Being reborn in Christ grants us a nature descended from God (no longer Satan or Adam) which is without sin, is perfect, holy, and is eternal life. Jesus fulfilled the Law and being reborn in Christ means that one in no longer under Law and has come under God's grace (because God loves us) (Romans 8). Sin no longer has any power, and there is no longer such as thing death for that person (John 11:26).
The sting of death is sin, and the power of sin is the law. (1 Corinthians 15:56, 1984 NIV)
See Colossians 2:10-15. (Jesus also redeemed our physical bodies, but our experience of that is delayed until the resurrection—the reason being getting new bodies prematurely would interfere with some people getting saved, Matthew 13:24-30. The rapture has Christians' bodies dying and being given new ones at essentially the same time.)