It can be puzzling why there is something rather than nothing. Saying God did it still leaves you to explain how he got there.
A while ago I had an idea (after reading an essay by Hans Moravec) that the reason is that mathematical facts have to be as they are, universe or not. Things like five being a prime number have to be so. Also physics seems to boil down to a bunch of maths so maybe all mathematical facts have be, our universe is part of this, this seems real to us and is the reason it's all here.
I spent a little while trying to write it up the idea with mixed results. Even so I find the idea interesting in that at least you can look at it as a hypothesis as to why there is something rather than nothing:
Hypothesis:
There is something rather than nothing because there are mathematical facts that have to be. These can form patterns including some that look like our universe and seem physical to us. And this is all that there is.
You can quibble about the definitions and details but presumably it either basically is the reason for existence or it is not. Also I think it is quite likely true as it fits with reality well and there do not seem to be obvious alternatives.
To illustrate:
Some numbers are prime and others not. This can from a kind of one dimensional pattern that has to be as it is, shown here with the primes in red
1 2 3 4 5 6 7 8 9 10 11 12 13 14
obviously the symbols are human inventions but the pattern of which numbers are prime would be the same if discovered in any universe.
A similar but more complicated two dimensional pattern is the Mandelbrot set pattern:
And the idea is that the universe is similarly something like a 4 dimensional pattern that exists in the same way:
with time as the fourth dimension something like:
This is similar to Max Tegmark's level IV mathematical universe hypothesis except with a different argument to get there.
I tried to write a version of this up more formally working with an analytic philosopy tutor, Phil Joyce, with the idea of sending to a philosophical journal. I did not send it off but here is a draft version (2011)
And the same thing with Phil's notes on it:
4th draft Phils response.pdf Size : 84.409 Kb Type : pdf 

There are some other versions out there. I'll post some more stuff some time...
(Appologies to the copyright owners of the above images)