Brainiac was on the verge of collapse.
In the comics, Brainiac was a purely logical being with no emotions. But in reality, if he truly possessed Level 12 wisdom, then he could fully understand emotions and simulate them.
Though this was unnecessary most of the time, understanding the behavioral logic of emotional Intelligent Life inevitably required taking emotional factors into account. So he knew that if human emotional vocabulary were used to describe his current situation, then "collapse" was probably the right word.
And if he were to describe the Justice League that had put him in this predicament, he would not hesitate to use all those insulting terms that he had once considered meaningless, rage-filled emotional outbursts. He even felt that human vocabulary was far too impoverished to properly describe this organization.
But collapse was collapse, and cursing was cursing. He still had to think of a solution. Otherwise, wouldn't he be letting those bastards get their way?
Naturally, Brainiac's first idea was not to follow the Justice League's plan. He wanted to solve the problem at its root: break free from this time loop.
But unfortunately, no Brainiac from any universe possessed the ability to manipulate time. More precisely, he was a third-generation creation, far removed from rules and origins.
Krypton's god, Rao, had created the Kryptonians, and the Kryptonians had created Brainiac. By the generation of the Kryptonians, they had already strayed far from Primal Power. By the time it reached Brainiac, he could not even touch its edge.
What source of origin and rules was closest to him? The Mother Box.
The Mother Box itself was really only a supercomputer, perhaps not even as advanced as Brainiac. But unlike him, the Mother Box was closer to the universe's origin, allowing Brainiac to draw closer to it