Let's try this on for size. Sorry for the length; I promise to be more brief if i respond later.
There's an infinite number of imaginable ways to explain our existance, our self-aware consciousness, here on Earth. It's that self-awareness part that seems to get humans into so much of a quandry. It seems unlikely to me that it all just happened for no particular reason.
Ditto for Christians. We just come to different conclusions about how. Or why.
As you say, there's no particularly conclusive evidence to absolutely explain any it. Yet. We have some predictions, some true theories, and as theories sometimes do, especially the better ones, they usually predict some measurable outcomes. Logical, yes?
I mean, if we suspect that a camera flash unit is present and operational behind a solid wall, (i.e.: we can't see it, but we think it is there) and we think that it's capable of making flashes of light when we press the remote button, well OK then. Could be other things, other sources, though, right? It could be a "flash-god" for example.
Especially if there's a large, noisy group of "flash-god'ers" over there, chanting loudly to drown your question out, and wanting to burn you at the stake for even asking any further questions!
But, we can predict that if it
is the flash unit, we would see a flash specifically when, and only when, we press the remote. We could also predict that the flash is the source because of the scientifically measurable type (spectrum) of light that we know that flash unit produces, and no other type of light. We could also measure the flash duration, which we predict is the same as the specs on the supposed flash unit.
All these measurable and observed and accurately documented light events are examined, and we can reasonably conclude that there is, with a high level of confidence, a flah unit behind the screen, but we don't KNOW for sure.
So. Of all the near-endless possibilites as to the formation for, rationale behind, and existance of, our Universe, scientists have made some non-supernatural predictions
(i.e.: that do not require a supernatural source), or an imaginary God. Of course theists can wilfully concoct a near-endless variety in their imaginations of alternate godly versions of our initial creation. Especially, they like the one about a white-bearded guy who made us in His image. Especially when so much power and political influence and prime real-estate are at stake!
But then, there's those pesky scientific predictions. You know, that if it
was formed as we atheist-scientists think it might have been, why then we'd expect to see certain key byproducts, certain event horizons
[love that phrase!], certain traces of elements, long-decayed but residual radioactivity, certain radio-frequency energies that we can detect even on our am radios or TVs
[go to an unused TV channel; the "snow" you see is, predictably, the ancient radiomagnetic traces of the Big Bang.].
Ditto for the many, many, ohhhh so
very many other aspects of the relentless and ongoing examination of our world, our universe. Most of them predicted by our theories that
if there was a Universe-starting Big Bang of the base element(s) we suspect (hydrogen, mostly), we'd see this or that. And guess what?
Scientific examination has pretty much found
exactly what they predict. How interesting, huh?
So, back to our basic discussion. No, we do not have conclusive proof of an event as we describe it. WE probably never will. We may, however chance upon some equations or some determinable process that does inexorably point it's well-lit finger directly at a Big-Bang event, or something else that is quite extra-ordinary. And, additionally, what we have found so far surely points clearly away from a supernatural occurrence. Who needs one anyways? Why?
Humans as we know them today may never evolve the necessary "brainial" IQ to even speculate or understand what might, in fact, already be laying right here under our noses. As I'm fond of pointing out, it's like my trying to explain the theory behind my DVD player to my favorite, quite bright cat, Dottie The Wonder Cat. She'll just never get it, frankly! And yet there it is, a working DVD player! And it's not automatically supernatural. There are other ratnioal possibilities!
On the other side of the argument that boils over relentlessly here on C-D's R&P fora, there is absolutely
no substantive evidence, no observable, empirical predictions that have been brought to the table, ever, in favor of
any of the near-uncountable mythical, supernaturally produced, coyote- or raven-god, or Christian god, or Muslim god or Chinese dragon gods. Or even our favorite, the Flying Spaghetti Monster god. FSM for short, BTW.
Why then should we even concentrate any residual energy on trying to fit our well-measured square observation results into a specific round receptacle hole, called Christianity? That's their tactic and strategy; to dismiss the problem observations, and pound the others into shape; their pre-determined shape, certainly not reality.
Why should we focus on that particular deity, or any diety for that matter? Where's the logic for that expenditure of precious time and energy?
We are no longer bound by the massive encumberances of the ancient uneducated age of superstition. Look at the biblical translations; rife with descriptions that match the intellect and scientific understandings of the time. They could not have even begun to describe the rapid oxidation of a chemical in the presence of air, to produce heat and light (i.e.: FIRE).
They looked up in fear, and assumed the universe revolved around the Earth precisely because they assumed we were motionless, and surely the sun was not. I mean, just look up! There it is, moving, and we're not! Proof!
So. It's not a simple case of decisions between only two polar opposites. We have the painstaking and logical design of ever-more precise measurement systems, followed by multiple observations by a growing multitude of independant rational well-trained observers. This is followed by a careful interpretation, via tools of statistics, direct measurment or deduced observation
(remember our flash unit?). We see if they might fit sorta-kinda, or perhaps
exactly, against our predictions.
We then come to reasonable conclusions, and we
always state the resonable limitations of our study design, and of our conclusions, and the larger implications. So, we narrow down the possibilities. In many cases, the conclusions exactly fit our theories, and it explains some long-hidden quandry, and we move on.
Against this, why should we be forced into accepting only
one alternate supernatural theory? Why is it a "this or that" model we must allow?
It's because the dogmatic and persistant religious types want to be able to dismiss our version, and show it as the only other alternative, leaving, some very poorly designed "default" position. Which, of course, is, conveniently, their's.
Finally
(At last! He's finishing up!), why limit ourselves to only the two diametrically opposing views? An atheist is not limited in this way at all. He simply looks at the godly versions: coyote, raven, totem pole, YahWeh, Mohammed, or whom/whatever. And he looks at the scant and now disproven evidence for those options, knowing there may be others, but these certainly don't fit the observations.
He's also not blind to the increasingly desperate attempts by fundy Christians to "defend the indefensible"; their foot-stamping insistence that the universe does, in fact, revolve around a flat earth, that we Insta-Poofed into existance long after, for example, the Chinese historians documented our presence. That vegan T-rexs

were saddled up and ridden by their happy human masters as recently as 2000 years ago, despite that there's no left-over evidence, and it's obviously patently foolish anyhow. And that any other version should NEVER be taught in schools.
Such stuff is not convincing to the rational and educated person, a category to which atheists are commonly attached.
He's likely also read some of the research summaries that show at least partial but positive evidence for a more empirical, more naturalistic world view, and he likes the logic and rationality of this version, so he simply dismisses the "nonsense" of Christianity, as he sees it, and moves on.
Get it? Why limit ourselves artificially, when there's so much to see, to learn, to appreciate under the warm illumination of the truth!
