The question of why do the cosmos exist could be expanded to "why does anything exist at all?" I think we take for granted that it just does and reality does not need an explanation in order to keep doing its thing.
For instance, life struggles to survive because death is the end of consciousness, or the nothing.
Really life struggles to survive only because that's a primary feature of evolution, and a product of that is the fear of death. If things weren't afraid to die, their genes would be removed from the gene pool pretty quick.