A big bang event could explain the reason why the universe expanded in the first place, but it does not explain the accelerating expansion of the universe currently, forgive me for my ignorance if any, but in physics I was taught that any object which moves or is in constant motion was acted upon by a force, and so if the big bang created an expansion it will be a constant expansion and not an accelerating expansion as is obtained presently, as there is a requirement for a kind of force to cause an accelerating expansion which is not explained by a singular big bang but by a continuous big bang, which could as well be infinite in nature.