Why is there anything? It is kind of conceivable that there could be no thing "existing" at all – no world, no universes, no consciousness. However, there is at least something; that is for sure, if none else is.
Let me clarify the question: The opposite of “there is something” is “there isn’t anything (e.g. observed)” but not “there is (e.g. observed) some nothing”. This is important to avoid much ado about nothing. “Nothing” refers to the absence of anything. “Nothing” is not another something.
If nothing were another something that “is”, this “something” would have to “be” precisely in case there is not anything (a contradiction). This contradiction is not the big answer; it is nonsensical to claim: there is either whatever else or there is still nothing, so something is always there, even if that something happens to be nothing. Such is crazy talk and not the proof of the impossibility of nothing; this is merely confusing different meanings of the term “exist”.
The correct answer is: Because it is possible!
This answer may seem wrong. After all, if the posed question were about any other system but totality, the given answer would be preposterously wrong: That something is merely possible does exactly not imply that it is necessarily actualized.
As pure philosophy, we are almost unable to grasp the answer. It is physics which presents the answer to us in a more acceptable form, although physics could have been expected to be the least likely science to do so: Physics, the science that started out to be squarely about things bumping around inside a world, but ended up showing that there are no such things, neither the former nor the latter.
Quantum mechanics brought the posed question into the realm of science. Although it is a pseudo question that depends on what you mean by “exist”, quantum mechanics kind of answered it anyway. It thereby turned the posed question into a lesser one:
Why is there anything possible? This question we may be able to answer. We will then finally know how a more intelligent species could possibly have known all along, as fundamental physics will then rest on epistemology, as it must, since all else is upside down.
And this describes my work: Like Marx took Hegel, who stood on his head, and put him on his feet, I work to take physics and turn it around from its upside down orientation, to put it on the only solid foundation possible, which is the head of course.