The Laws Of The Jungle

The proliferation of Aether in this universe was not to create life, it was simply to make it stable enough for Rowan's dimensional soul and flesh to enter without cracking the universe open like an egg.

He could assimilate a universe easily, but it was a different case when he began flexing his will or even manifesting his presence, no material universe would be able to contain such power, and if he wanted a place to be able to digest his gains so that he could prepare for the inevitable chaos that was about to descend upon all of reality, then he needed this universe to be more robust to carry part of his weight.