Stephen Hawking was a extraordinary scientific talent, by all accounts. I put it like that because it's the judgment of his peers, who are the only ones who count: most of us aren't qualified to say (like a lot of people, I read A Brief History of Time when it came out and thought I understood it, but I probably didn't).
However, he did impact popular consciousnessness and culture to a remarkable extent. Partly that was because there was something very potent about the image of a wheelchair-bound figure, unable to speak and reliant on technology to keep him alive from moment to moment, but with a mind that could span galaxies. Partly it was because he was fun – he understood people's fascination with him and played along, to the extent of appearing in hit shows like The Big Bang Theory.
And partly, for Christians in particular, it was because he was tantalisingly vague about religion. He said in A Brief History that if we ever discovered a 'theory of everything', it would be 'the ultimate triumph of human reason – for then we should know the mind of God'. A flurry of speculation regarding his religious beliefs followed. But he was later to explain that by saying, in an interview with the Spanish paper El Mundo: 'Before we understand science, it is natural to believe that God created the universe. But now science offers a more convincing explanation. What I meant by "we would know the mind of God" is, we would know everything that God would know, if there were a God, which there isn't. I'm an atheist.'
It may be, in fact, that his views evolved over time. I'm told he attended St Andrew's St Baptist Church in Cambridge on occasion years ago, and his first wife Jane was a Christian. Journalist Andrew Graystone recalled today on Twitter interviewing him once, saying: 'I asked him at length whether he believed there is a God. He refused to answer the question. When I asked him why, he said "If I say I believe in God, everyone will immediately claim that I believe in the same God they believe in. So I won't say at all."'
I asked him at length whether he believed there is a God. He refused to answer the question. When I asked him why, he said “If I say I believe in God, everyone will immediately claim that I believe in the same God they believe in. So I won’t say at all.”— Andrew Graystone (@AndrewGraystone) March 14, 2018
Certainly he doesn't appear to have ever believed in an interventionist God, saying in a Reuters interview in 2007: 'I believe the universe is governed by the laws of science. The laws may have been decreed by God, but God does not intervene to break the laws.'
And he told El Mundo: 'In my opinion, there is no aspect of reality beyond the reach of the human mind.'
So was Stephen Hawking an atheist by the end of his life? Probably, though that answer might not be the whole story.