It's a metaphysical question.

Metaphysical cosmology is the branch of metaphysics that deals with the world as the totality of all phenomena in space and time. Historically, it formed a major part of the subject alongside ontology, though its role is more peripheral in contemporary philosophy. It has had a broad scope, and in many cases was founded in religion. The ancient Greeks drew no distinction between this use and their model for the cosmos. However, in modern times it addresses questions about the Universe which are beyond the scope of the physical sciences. It is distinguished from religious cosmology in that it approaches these questions using philosophical methods (e.g. dialectics).

Cosmogony deals specifically with the origin of the universe.

https://en.wikipedia.org/wiki/Why_there_is_anything_at_all

You can theorize about it, but for most theories, you aren't likely going to be able to do much to test them.

We just don't have any knowledge that we can get from the world that would let us make much of a call on it. Nothing we're going to learn is likely going to let us provide an answer.

It also probably won't provide much useful predictive power about the world, which is normally why we want to gain knowledge.

It's like asking whether there are decoupled universes that we can never interact with, or why the specific physical properties of the universe are the way they are -- we can maybe dig deeper within physics, come up with simpler or more-accurately-descriptive models but at some most-primitive level, that falls off of physics and into metaphysics. At that level, physics can only say "this is the way things work", not why.

So I'm not going to worry too much about it. There are hard questions that we don't know the answers to that are within the realm of testability, and that do have predictive power.