I think the whole issue can be summed up in this particular question and answer.
Why was this so important?
Well it’s probably not important for curing cancer, or knocking down enemy missiles, or speeding up your computer. But it is important to the future of physics and cosmology. The universe is controlled by two fundamental laws: Einstein’s gravity theory (the General Theory of Relativity) and Quantum Mechanics. Stephen argued very convincingly that the two (GTR and QM) were on a collision course. Gravity and Quantum Mechanics were just plain incompatible. One or the other would have to give, at least by Hawking’s logic.
Stephen was wrong, but his astonishing question has changed the history of physics, and there is much more to come.
Yup! There's definitely more to come...