In every dimension, there were hundreds if not thousands of Managers all overseeing their universes, taking care of their universe and monitoring it to avoid its inevitable end. They weren't omnipotent, but most of them are more powerful than a regular human on average.
Universe 31 and Universe 69 had already fallen, and their Managers were removed from their posts since they were incapable. And now, Universe 1 is at risk of being deleted. While they survived the first wave of the World Eater, the second wave was bound to come. There was no way that Universe 1 could get out of the inevitable predicament.
During the first wave, Universe 1 fought with everything they've got, and it resulted in their victory. However, every race died because of that, and only Earth was left with inhabitants. Now, with the upcoming second wave of the World Eater's invasion, they were bound to lose.