Well, no model of big bang cosmology says something about how energy came to exist in this space as well, and based on the principle of mass-energy equivalence we do not know how stuff came to exist. It is important to keep in mind that the Big Bang cosmology was a theory originally described by a catholic priest (Georges Lemaître), this theory is closer to theism than its direct (academic) competitor in the past, the steady state cosmology, that predicted an eternal universe, basically it says that time and space existed since forever, in which new matter is created every moment.