Well, that's where they were when Jesus went "down" there -- he broke the gates of Hell (not Hades) and pulled out the righteous. If they were righteous, why were they in hell?
All of this is extra-scriptural Tradition, isn't it? If so, then I can't possibly know how this idea came to be. I don't know of any evidence in the Bible that supports the idea that any of the righteous ever went to hell. There is evidence, however, of quite the opposite:
2 Cor. 5:6-8 : 6 Therefore we are always confident and know that as long as we are at home in the body we are away from the Lord. 7 We live by faith, not by sight. 8 We are confident, I say, and would prefer to be away from the body and at home with the Lord.
Paul makes no mention of going to hell first. Besides, IIRC, in the icon I saw, along side of the OT righteous in hell were standing Apostles! What were they doing in hell?
They are not in hell. They have been rescued by Christ and welcome Adam and Eve, who are being rescued. The hell is represented by the hole in the ground.
There is is a dispute I had with Kolokotronis once. Have the OT righteous been assumed into Heaven in the similar manner as Elijah, upon their death, or have they been rescued by Christ in the single historical timeline on the Holy Saturday?
Unless they repented, I believe they would all go to hell. Unless they have forgiven those who trespassed against them, they could not ask God to forgive their trespasses. Those who showed no mercy can expect no mercy, the Scripture says.
Adam and Eve did not repent, so they would be in hell. Moses murdered a man in revenge. And what is your definition of salvation? It is to accept Jesus as your God and Savior? I don't think there is another way. Well, they didn't know Him -- even if we speculate that they would have recognized Him, they still didn't accept Him because they lived before He did, so they died without knowing Him and without specifically accepting Him.