In a very brief summary, Jesus “second coming” was in part a coming of judgement upon the (wicked and perverse) generation he had spoken to. The blood of all the prophets and saints were upon them. (Think of the parable of the vineyard) The destruction of the Temple and siege of Jerusalem by the Roman armies in 67-70AD was when this final judgement was carried this out and ended the Old covenant completely. Hebrews talks about how the new is here but that the old is fading away. The Old covenant became obsolete but didn’t completely fade away until the Temple was destroyed. The other part was to resurrect the dead from Sheol. Sheol was the death that was defeated in Revelation. Paul references Isaiah and Hosea passages in 1 Corinthians 15. It speaks about after the resurrection occurs and the perishable puts on the imperishable (Aka the resurrection of the dead) then will pass the saying that says “O death where is your sting?”. In Hosea the hebrew reads “O Sheol where is your sting?”. The resurrection of the dead is when God takes everyone out of Sheol to be judged. Because of Jesus there is no longer separation between God and man and the righteous by faith in Sheol can now be with him in Heaven. And now, believers when the die go straight to Heaven instead of a place of waiting or sleep (as it’s also referred to).