"Why are we here?"
What is the value in knowing "Why are we here?"
The universe is governed by science. But science tells us that we can't solve the equations, directly in the abstract. We need to use the effective theory of Darwinian natural selection of those societies most likely to survive. We assign them higher value.
You've said there is no reason to invoke God to light the blue touchpaper. Is our existence all down to luck?
Science predicts that many different kinds of universe will be spontaneously created out of nothing. It is a matter of chance which we are in.