Because there is a law such as gravity, the universe can and will create itself from nothing.
Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist. It is not necessary to invoke God to light the blue touch paper and set the universe going.
But why would this constitute news except to story-dry science journalism? In what sense does he have any more authority on such a subject than, say the Pope or authors of any sacred texts?
Hawking argues, perhaps proves, that our something could have arisen out of somebody else's nothing purely by self-driving physical processes. We have no reason to challenge that assessment (and haven't read his book yet). But the fact that he's a famous physicist gives him absolutely no 'authority' about such issues.
For one thing, God could have created the rules of physics and the starting stuff in which this happened.
The point is not to get into the God food-fight, but simply to say that while we might wish to invest authoritative wisdom to someone, to cure our angst for an answer, it is not to be found in this kind of scientific pronouncement (and likewise for those who say that since they can explain everything by evolution, therefore there's no God).
Everyone can have an opinion, and can rest it on whatever facts s/he takes as most cogent. Scientific arguments may be able to account for a phenomenon. As scientists we have perhaps a duty to point out when religious arguments about the material world are simply wrong (for example the young-earth or the Intelligent Designer arguments). There, authoritativeness has meaning and it's OK for the news media to report it as such.
It's also fine to cite Dr Hawking's reasons for why what we call the universe could have self-ignited. But it is a continued misrepresentation of science, especially by journalists, to headline scientists' opinions as if they carry authority, when in fact they don't, and can't. Making that kind of hero, to sell copy which is the bottom line here, is wrong.
We should have a more proper public understanding of what science actually is, and what it isn't. Science journalists should be more properly trained.
Even if in a given case we would choose to listen to someone who knows a lot about the world to see why he thinks as he does.