The problem is that, according to our present best hypothesis, the universe began from a singularity, that is, all of it existed in a point as close to infinitely small as physical will allow,
And the singularity cuts us off from any information about the physical circumstances, if any, that may have existed earlier. We simply have no access, no way of finding out.
My own thinking is that the contents of the Big Bang must have pre-existed. If instead there was a genuine absolute nothing, then it would have neither matter nor energy, neither dimensions nor qualities of any kind. It would not be an empty something, it would absolutely not exist, and there would be no place and no time at which anything could happen.
We learn more every year, sometimes a little, sometimes a lot. Stay tuned.