I am an atheist, and i think you are correct that people believe in God to give their life a meaning, and that it is a waste of time.
However, you could equally say that the big bang is scientifically impossible, as no laws of physics were obeyed and matter was just mysteriously "created", just as you say that it is scientifically impossible for "one man" to create the world.
I do though, have much more respect for a theory based on science than any crazy randomly thought-up creation story. I think we just have a long way to go before we understand everything though, and until that day comes, god will always have a place (for some people), because uncertainty means that supernatural ideas can't be disproved.
Some people simply cannot grasp the idea that we just "are" and chose to believe that something put us here for a reason. I don't think they consider it to be a "man" though lol.
It was just curious speculation years ago, and then people wrote books (bibles) about what they thought. Now, it's all blown up out of proportion and people chose to live their lives around the idea of a God, which I think is silly.
And yeah, i think when you die that's it too. Lots of people just like to believe in a god for that reason as well- they feel comforted by the idea of a heaven, and don't want to just rot away. Like my mum for example. Haha.