Despite Logical Positivists and others who will tell you that some questions are not fit to ask, I hold it as a personal truth that all questions that can be framed can be asked, and even from nonsense we can sometimes learn something, such as where we are personally mistaken in our understanding.
Given that, I say this looks like "what Martin Heidegger has called the fundamental question of metaphysics"as described by Art Witherall, so it has quite a pedigree! But its roots lie in the unresolved question of universals which dates back to Plato and Aristotle. See Problem of Universals on Wikipedia
One argument [given in answer to the question by @Saul] is:
".. if Nothing could be, then it would inevitably be Something - giving us a contradiction with our initial premises, thus demonstrating that Nothing cannot be."
But that has a whole bunch of issues about what kind of something, it seems on the face of it that it bootstraps Being, but really it just demonstrates the contradiction, not how the contradiction enables existence to be.
My understanding of the question is that the OP means how does it happen that we are here when so much is necessary to explain it? How does the Universe/Multiverse come about from an assumed earlier state of nothingness, or as an alternative to that state?
It is an expression of amazement, I think, and rightly so. And right up there with the top questions about us.
My answer is this:
I say there is a state I will call virtual that is very similar to the ideal of universals.
The nature of the virtual is that something of it is inherent in any reality [Axiom 1], at least, where it is created as a consequence of relationships. Therefore, if we consider a situation where no thing is real, nothing, no material reality, no time, no space, no God, we can see that this would be a real state of affairs, if it were so it would be a real null. So it would also imply a virtual state of affairs as the ideal of nothingness, which is the same as a null relationship. This is the something which the reality of nothing forces into being. It is not much, just a virtual link between nothing and itself.
It would be a dead end, going nowhere, if it were not for the second axiom concerning the virtual.
The other nature of the virtual is that whatever is logically implicit in one state [instance] of the virtual necessarily follows on from that state. [Axiom 2]
From axiom 2 we automatically, and necessarily, get the virtual state [predicate] of being. This virtual state is a relationship between the spirit [meaning/essence] of nothingness and the spirit [meaning/essence] of being. This is the first non-null relationship, but it is not a concrete thing, it is a virtual, abstract, thing, that exists nowhere and at no time.
That might not be perfectly argued, but the gist of it is, I think, valid.
The implications of this are many, but there are then even more steps to arrive at material existence. Which might include:
1) Number is a clear virtual consequence, and I imagine is still counting toward infinity, without being any closer, and in doing so provides a tick that is one measure of absolute time.
2) Dimension is a natural consequence of number, and so another virtual feature of existence, one that creates a multi-dimensional void.
3) Virtual time is only one thing happening after another, so having happened they remain, which is eternal.
4) Godel's Incompleteness Theorem suggests some things are unanswerable by mathematics alone, so there is a need for something like a universe to try things out and see what happens.
5) Consciousness could be in the relationships between the contents of mind, making it a virtual quality, rather than a physical quality of concrete brains.
6) The Big Bang takes place in the multi-dimensional void, creating a 3d Universe that expands as the surface with a common radius from ground zero. That surface is always now, and holds all the matter/energy. Consequentially yesterday is gone, and tomorrow not happened.
7) Material time is actually absolute, so all Relativity is about rate changing, not time. (space and time not really interchangeable, and no time travel)
8) Quantum effects are not interpretable as a block universe, but require something akin to the Transactional Interpretation to explain Young's Slits.
9) Other weird stuff happens, not yet accounted for by mainstream science.
10) Maybe death is not the end, except for our bodies.
So there you go. Maybe it is not all exactly correct, or is heretical in places, but that is the joy of asking questions, especially impossible ones!
PS. I am in no way qualified to claim any of the foregoing.