AGREED -- great question. Why does anything.. anything at all exist? Why not purely and utterly - NOTHING!
This is probably better in the Philosophy section.
I think most PRESUME some sorta ordered Universe (including a multiverse) exists and then proceeds from there.
This is no doubt what Cosmologists and Pysicists mean when they say "nothing" -- they actually just mean a Universe that already exists but is in a very low state of energy and entropy.
But when the Philosopher asks "Why something rather than nothing" -- they mean truly nothing -- No laws, no matter, no order, no energy, no multiverse, no dimensions - not any one thing.
And this is perhaps the most profound question mankind CAN ask. Sadly, many people scuff at this, throw up their hands and say "How can we know!"
We also can not simply assert that the Universe "always existed" because this question asks "Why?"
I would end with saying that we should continue to wrestle with this question but as long as we deposit physical explanations, those explanations will need further explanation as to why THEY exist.
What is needed to end the causal loop is a metaphysical source -- A non-physical source that because it is not physical, doesn't need further explanation.