And yet this is the very heart of the matter for those who actively believe there is no G-d. All mass in the universe was concentrated in one little ball. We don't know why or where it came from, but we certainly know G-d had nothing to do with it! Then for some unknown reason it blew up - NOT because of G-d, that much is certain! Then one day life just sprang into being - which is perfectly natural! Then that life became more and more complex over millions of years, even though much of that complexity involves expending energy with no return over long periods of time - just by chance, thank you! And that complexity led to different species, different genera, different phyla, different kingdoms - even though many of these changes necessarily make creatures not inter-fertile - purely through chance.
By contrast, those believing in a Creator needs must believe only that something operates beyond our universe, beyond our perception. The description of that Creator, and the degree to which it touches our universe and lives, are merely nuances in ideology. I have no problem with people believing that there is and can be no G-d, ever, but I am most amused when they ascribe to themselves great wisdom for doing so.