Board Thread:Questions and Answers/@comment-6312663-20130302175900/@comment-4651179-20130305185840

Because there are these two cosmic entities, which represent the Marvel Universe and DC Universe, and are like "brothers" fighting. They put their champions to fight, and the "brother"/universe which would lost more battles would be destroyed. But Captain America and Batman managed to make them be in peace once more and stop this competition, firstly the two brothers decided to become one (the famous Amalgam Universe) but then they were convinced to be separated again, but they were in peace again.