That sure would be ridiculous, if that were the theory of the Big Bang, but of course it's not. You won't be in a position to debunk it until you are conversant with its most basic concepts.
The equivalent dismissal of Christianity would be, "there was this old man with a white beard, who then became God somehow, and who then somehow created the universe and then man."
Okayfine. So I am not conversant with all the details of Big Bang theories. It is still part and parcel of scientific method to employ probabilities and predictions. That's really all we have to work with.
Predictability works very well when one is dealing with a universe chock-full of design at every turn. If everything has been derived from, and continues to be derived from, a mass of undirected energy, then one must throw predicatability, and even science itself, out the window.
The recurring mantra "religion is not science" finds an equally valid counterpart in "evolution is not science" insofar as the latter can only extrapolate assumptions based on past, unpredictable processes.