When Christ died, the Devil took His spirit prisoner to Hades (Acts 2:27, I Pe 3:19). Since death was the penalty for sin, Jesus was under no obligation to stay dead. Therefore, the Devil’s act of taking Jesus’ soul to the prison of Hades amounted to kidnapping God’s son. That was an act of war, and both Jesus and God were justified in resisting Jesus’ incarceration with force. According to the parables, Jesus was stronger than the Devil, overcame him and spoiled him of his goods (Mt 12:29, Mk 3:27). Among other things, Jesus took the keys of Death and Hades (Rev 1:18), and He thereby gained power over the dead. Because of Jesus’ power over the dead, He has power over every man (Heb 9:27). Because He now has a lawful claim over the soul of every man, He plans to raise the dead and restore all things (Acts 3:21).
In order to restore all things, God must restore peace and harmony, but He has irrevocably given men free will. In order to restore the pristine peace and harmony, those men who choose to introduce chaos by refusing to obey God must be removed from the earth. In order to determine who is fit to participate, God has decreed that there is to be a judgment where each man’s works can be examined. This judgment will determine those fit to enter the world to come. How is fitness determined? Certainly not by perfect obedience (Rom 3:20), if Christ died for all men and God is just, how can He justly send men to hell? Since Christ has died and provided a legal basis for justification, God’s decision is based on grace AND truth (Jn 1:17). However, grace does not forbid punishment for those men that are unrepentant and willing to obey truth. Many people have shown a disposition to disobey. Because of their willful disobedience, God can do nothing further for them (Heb 10:26), for He has irrevocably given men free will (Ro 11:29), yet some men are willfully disobedient. If God released these willful sinners on the new earth, they would continue their willful ways. We know that is the case, for after God destroyed the earth by flood, the angels that sinned appear to have continued their sinful ways, since their giant progeny appear, even after the Flood (Gen 6:4, Num 13:33, Dt 2:20). It was not until God imprisoned them (II Pet 2:4) that the production of giants ceased.
Because Jesus now has the keys of Death and Hades, God can now hold the Judgment (Jn 12:31), because Christ has lawfully obtained possession of the souls of men and He is going to raise the dead and restore all things. There is eternal hell because some men of free-will will not accept God’s rule and He is not willing to ruin the world to come by letting willful rebels run amok on it.