Good, because in the next part, these immortal beings soon realized their planet was dying. In their wisdom, they discovered the planet relied on that cycle of their living and dying to keep all life going, but because they stopped dying, the planet couldn't maintain this cycle.

So, with their cycle ended, they came up with solutions... none of which were to just accept dying again. Why not? Lots of people I'm sure imagine immortality as a great thing. And from there, they decided to start fusing with other planets before they began to generate life, putting that energy into their planet.