Leibnez asks, "If God does not exist, why is there anything at all?"
It's not a meaningful question. You can ask why is there anything at all, whether god is in the mix or not. And having god in there doesn't answer the question because you can still ask, why is there god?
If there are an infinite number of universes with an infinite number of configurations of the laws of physics, then it is inevitable not only that a Supreme being exists but that an infinite number of supreme beings both good and evil exist. It is inevitable that with an infinite number of universes there must be an infinite number of universes where these supreme beings can exist in more than just one universe. Therefore it follows if all possibilities are true that an infinite number of times an infinite number of evil Supreme beings have consumed the entire multiverse and would have destroyed it. Since we are here speaking to one another that is not possible. Therefore the multiverse refutes itself. The problem is that they start with an infinite plurality to explain the universe we see, rather than a singularity, while Aristotle pointed out long ago that a first cause is the only philosophically logical answer.