God gets my vote for top engineering achievement. When trying to compare the biblical versus scientific explanation of creation, I have to wonder if maybe there's room for both notions. Science explains how the universe came into being, but not why or the reason it happened. On the other hand, the theologians aren't concerned with the mechanics of creation. For them, the mechanism or method is much less important than the reason and motivation behind creation.
Science says that there's a cause for every effect.
In the case of the big bang theory, it isn't possible for science to determine the cause. The evidence of the cause was permanently transformed at the moment of the big bang. Science may well prove to be a dead end street - at least the science we humans now practice. So to answer your question, finally, I believe God was the cause behind the effect, that God is the cause of creation. Please be at peace.