If God does not exist, then all that exists is matter and energy, and all things can be explained by the forces of matter and energy. A person who holds such a position can ask a myriad of ‘What?’ questions, as in “What is the condensation point of mercury?’ or ‘What is the speed of light through water?’ or “What is the weight of a golf ball on the moon?’
But an atheist, who is by definition a materialist, cannot ask ‘Why?’ questions, for these questions have no meaning in the atheist system. If all that exists is matter and energy, we cannot ask ‘Why is there something, rather than nothing?’ If there is no intelligence behind an act, we cannot ask ‘Why was a golf ball hit on the moon?’
The atheist cannot ask ‘Why is there a universe?” for why is not meaningful when all we have is what.