@DZ-Jay
"What's it all for"
That supposes the existance of a superbeing to have had a purpose for it. An aetheist would have to believe that there IS no overriding purpose for the universe.
A theist would also have to accept that it's possible there's no purpose; we could just be an accident or a side-effect. They could also have to accept that we'll never know- any superbeing so... well, super that they could create a universe would surely have inconceivably complex purposes for what they set out to do?
A Scientist would say that there's no solid evidence for or against a superbeing creator. But as no evidence *for* has been found and the chance of us being able to understand its motives if there is a superbeing are so small- as well as the extra complications that would arise (Why is the superbeing there?) they'd probably stick to working on the presumption that there isn't one- a presumption that would be changed as soon as there's evidence for a superbeing's existance.
"Why are we here"
Isn't that pretty much the same as the first question? I guess we're here because of infinitely complex socioeconomic and biological factors stretching back for millennia. Because if you weren't here now then the laws the universe runs on would have been different. We're here because there's nowhere else that we here now could be.
"and so briefly"
Because we don't look when we cross the road. Because we're mortal- we run out of time. The idea that it's briefly is only one of scale- on the timeframe of a fruitfly or a bacterium- even ones that live within us and without which we wouldn't work properly- we live for vast periods of time. Compared to an atom of Francium you exist for an almost infinite length of time.
If you're meaning so briefly in terms of geological time, think of the next stage up- planetary development phases. Then the next- the formation and destruction of whole Solar systems.
Religion is one big ego trip. It supposes that what we see is the "right" way of seeing things, that our concept of time is the right concept of time and that we've got a purpose. We're tiny on a universal scale- or huge on even the scale of what we can mass produce. I'm something like 45,000,000 times taller than the transistors in the machine I'm using to type this, and I'm one 4.7x10^-20 of the galaxy- of which there are billions.
Time-wise, in a single 75-year human life 1,793,045 francium atoms could have been created and disappeared. Earth will have travelled 43,803,000,000 miles.
Any scale in between those- and even outside those- is equally valid.
That we're here at all is the product of a billion billion billion variables- all of which had to be absolutely right. All ~10Octillion atoms in your body had to be arranged exactly where they are, the physical rules behind it all had to be correct. Your surrounding atmosphere had to be right to not make you burst. The whole world had to be the right size just to support that atmosphere- and there had to be billions of years of history to get these uncountable atoms in just the right configuration for you to be typing.
That we arose from such a complex, vastly chaotic system is surely a greater puzzle than knowing the mind of a superbeing who would have such a complex system beyond them? And surely to simplify it to "God did it" is just an insult to the beautiful structures that have risen almost randomly from the chaotic mass of atoms as well as to the human mind- a mind that has created artificial structures and systems that allow us to comprehend such infinite variables?
Sorry, I'm probably rambling or ranting. But the universe is big enough and beautiful enough to be amazing and miraculous without a God.