The question; "How did something come from nothing?" seems to come from the theist conjecture of a time when nothing but God existed. Then along comes an atheist that removes God from the conjecture leaving the theist with nothing existing, and he says; "How can we get from nothing to what we see now." What the theist fails to see is that the atheist didn't start with the theist conjecture which made God necessary. Deep thought isn't necessary for an atheist. But if he does think about it, he must conclude that the Universe is eternal. So when all is said and done both the theist and the atheist must conclude that something is eternal. To the theist, that something is a God which he can neither see or prove. To the atheist, that something is the Universe which he can see and is obvious.
When someone tries that on my I ask them where God came from. Of course they will say he was always here. When I point out that something/someone had to make him they usually walk away. If they push the matter I tell them that if they can believe that God was always here I can believe that something came out of nothing.
But why is there anything, I.e., why does the eternal universe (defined in the widest sense - multiverse, potential for time and space to come about or whatever) exist, as opposed to absolute nothing? Never managed to get my head aroumd that one. Of course theism is just a way of pointlessly obfuscating that question.