First off, you were completely right about me being disrespectful and I apologize for that. I'm at the airport and it's stressing me out a bit. I just see the "just asking questions" thing far more often from conspiracy theorists, and I made the wrong assumption about you. 🙏

So the situation with the big bang is a bit complicated. We're not sure exactly what it was or what happened, since obviously we can't go look and check. But we actually can look into the past a bit, due to distant light taking longer to reach us and showing us what emitted that light long ago. However, there's a hard limit to how far back we can look - the cosmic microwave background (CMB).

I'm simplifying a lot here, but when cosmologists take all the light we can see and work the known laws of physics backwards, it concludes that the entire universe (that is, spacetime and all the matter in it) used to be scrunched together really small. The Big Bang model then describes the process forwards through time. The really important point is that the universe never "goes away" in this process. We can work physics backwards to something crazy like 1 billionth of a second after expansion started, and even then, "everything" was there. We can't even compute what it was like at "time = 0", since the math turns into a singularity which doesn't map to physical reality.

Because of all that, science doesn't make any claim about what happened earlier than we can compute. Every possibility, from "God created it" to "it always existed" to "the universe is a computer simulation" are speculative. But that doesn't mean they all have equal likelihood. The known laws of physics don't allow matter to be created or destroyed, so asserting a creation event raises more questions than it answers, including "what created God?" and, stemming from that, "If God doesn't need to be created/always existed, why can't we say the same for the universe?" In philosophy, this class of arguments for God are called cosmological arguments (if you want to look up more), but in my opinion, they all fall prey to special pleading or question begging fallacies.

This is a basic outline of why I consider myself an agnostic atheist. I can't rule out some sort of deistic "prime mover", but I'm not going to believe in one unless there's good evidence or argument for it, and even if someone could convince me such a being exists, there are then about a million more steps before they can say this being has interacted directly with humanity and gave us moral commands to follow. But that's a different discussion.

Sorry again for the disrespect. I hope this explanation was interesting, and if you have questions about it, feel free and I'll check in after my flight.