If you think Hitchens was a great thinker, you haven’t delved very deeply into philosophy. I’ll give you he was a powerful, galvanizing writer, and could be a joy to read, but that is very different from saying he had anything original or profound to say.
He had many controversial opinions besides his views on religion, e.g., his support of the Iraq war, and neo-conservativism in general. And though I personally supported his criticism of religion, even there his arguments were somewhat flimsy (I would recommend over him any of the other so-called four horsemen of the Apocalypse, Dennett, Harris or Dawkins). For example, he had to be very selective in his facts to make the claim that all religions tend to lead to violence, and outright blind to facts to imply that no non-religious nations are or were. Given that one of the major scientific criticisms of religion is that it tends to bend the facts to fit a preconceived conclusion, it’s rather ironic that God is not Great is full of arguments like these. You might say it was written with a fervor that bordered on the religious.
As for his dying young, of course it was unfortunate, but anyone who smokes and drinks in excess is asking for trouble. He was too intelligent and informed not to understand the enormous abuse he was subjecting his body to.