First of all, Big Bang is still a theory, so it might raise some doubts if we are to use a mere theory as a basis for determining the origin of everything. However, I'd love to share my views about this thing, since I believe that any theory will end up to the same conclusion.
Big Bang, according to Lemaitre, begins with a superheated sphere of energy that later on explodes, which is quite plausible, as depicted with the irregular scattering of galaxies and stars. However, one might argue that the probabilities of a cluster of energy will form a ball of superheated energy is very low, what with the unquantifiable, abstract energy roaming the four infinite corners of the universe. I believe that the universe had a huge singularity before the origin of everything, otherwise, there wouldn't have been enough gravitational force to have a massive ball explode that will start everything, but that's not the point.
Even with the supposed strong gravitational force of the universe's singularity, this is infinity we're talking about, which uses the "expanding universe theory" which is more plausible for me. Thus, we can say that the probability of energy gathering together is 1/∞, making it so unlikely that even if it will form on its own accord, the duration before everything will form would raise very exponentially.
However, despite the 1/∞ chance of having a random superheated sphere in some part of the universe, it still happened, and in a surprisingly short duration of about 17 billion years. No matter how humanity denies about this, this is where the immaterial comes in.
The probabilities involving infinitesimals are highly impossible, and yet it happened. Like what our asker said, what if the factor who was behind the extravagant feat of the formation of everything despite of 1/∞ probability is God? A celestial and a supernatural being?
First, a good number of scholars have concluded that the idea of God making the universe is absurd. However, one might argue that the Bible only applies to the Earth, and is defied at a macro scale. What if God meant this to happen that way, knowing humanity back then doesn't have the knowledge capable of scouring the universe?
Another thing is that taking the Bible's words literally can really make someone confused. What if God intended this to happen, to conceal the truth until human is capable of understanding it? The creation of light and dark, and the explosion of the superheated sphere exploding into the universe, resulting to mingled bright stars and darkness, they're relatively connected.
With how the Bible depicts how God makes different things, He might even be behind the pressure, temperature, and the singularity itself. Another thing is that if we're to consider metaphysics, we can ask this to ourselves: what if God created the universe through the Big Bang?
Three of God's descriptions include omnipresence, together with omniscience and omnipotence, so one might argue that God is ultimately everywhere and not disappearing at all, which raises a possibility that God is the energy; the omnipresent thing in science. If this is the case, there's a chance that God created the universe through the Big Bang, or through Himself.
These facts might also explain how this particular Earth came into existence, what with all the other substances and structures that came into being, although in a much smaller scale, since the numbers concerning this are finite. Thus, even if we get the gist of the theory of everything, this would take a whole lot of information to clarify every aspect of it, especially the mind-boggling enigma of infinitesimals.
While I entertain the continuity of human science, I believe that no matter how we research, unless we consider the other side, be more open-minded and think outside the box of concrete science, it would take centuries for us to figure it out, or worse, never figure it out at all.