Christians [let just assume most who believe in a god creating the universe] claim that nothing can create everything. Hence they insert a god into the argument. However, it must be noted that inserting a god into the argument only causes me to ask where does the god come from. Typically, the god would need to be
non-material (unseen), eternal (without beginning or end), and it had to be omnipotent (have the amazing ability to create everything from nothing) [source]
The latest theory of the beginning of this universe is the big bang theory. The first 10-43 second is the Planck epoch. Of course, there is ongoing active research hoping to have better understanding of epoch.
Today's science has not discovered what happened before the big bang. No one is claiming 'nothing has created everything'. The Big Bang is a singularity. We just don't know anything before the big bang yet. What is so hard for Christian to say "I don't know"?
It is extremely human centric to think that if there were a creator, the creator would create the universe for human and pay particular attention to human. By the way, why then our Sun is not at the centre of the Universe? Why then the Milky Way (our Sun is one of the many stars in Milky Way) is NOT at the centre of the Universe?