Didn't Christ conquer death, hell, and the grave?

There was a question on here, might have been yesterday or the day before asking about paradise and heaven being two different places. The best answer stated that they are different of course, but that the born again dead still go to a holding place in hell to await the resurrection. How can this be? If the bible says in 2 Cor. 5:8 that to be absent from the body, and be present with Christ, and Christ is seated at the right hand of power, which is God the Father in heaven, then how can we still go to a holding place in hell? What did it mean then when He descended into the lower parts of the earth and led captivity captive when He ascended on high? Doesn't this mean that Christ by conquering death, hell, and the grave that Christ removed paradise from hell and took it to heaven with Him? If not, then the devil it seems would still hold the keys of death, hell, and the grave. Can someone shed a little more light on this topic. Thanks!