Every cell, virus, plant, or animal mutation or characteristic is explained by Natural Selection.
It’s almost like there is some motivation for it to make sure life exists and survives. But why do anything at all? If there is a God then it makes sense that it was put in place for life to exist but if there is no God then why don’t we just have a universe of non-living matter?
I’m not sure that there needs to be a any grand cosmic reason for life to exist. Life could just be an accident of random events in our little corner of the universe.
Natural selection offers an explanation for how life changes across generations in response to challenges in the environment. It does not require a plan, just that the outcome of a chaotic process (reproduction) creates mutations that produce a slight edge, or at least no reduction in reproductive efficiency.