Due to the reality/time changing events of Crisis, Hitler was able to bring about Ragnarok, which the JSA was trying to stop. They were all trapped there for eternity, fighting the same battle over and over with the exception of The Spectre, Dr. Fate, Power Girl and the Star-Spangled Kid.
This was supposed to be the final story of the Justice Society. They were all in limbo until 1992's Armageddon: Inferno in which they were released back into the DCU.