In 2013, Google was negotiating to acquire , and Facebook was interested too.
While was visiting California, invited him to dinner.
Hassabis used the dinner as a form of test.
They spoke about AI, and Zuckerberg was enthusiastic. Hassabis then moved the conversation to virtual reality, augmented reality, 3D printing, and other emerging technologies. Zuckerberg was pretty enthusiastic about those.
Zuckerberg was excited about AI, but he treated it as one important technology among several.
Hassabis later recalled: “That told me what I needed to know.”
He went back to Larry Page and moved forward with Google instead.
That's how their alleged dinner went down.
Source: Sebastian Mallaby's Wall Street Journal excerpt from The Infinity Machine, which attributes the story to Hassabis. A 2015 interview with Hassabis describes the same underlying difference between Zuckerberg and Larry Page.
Regardless of how it actually happened, the key point remains: if we can build sufficiently great AI, it will be such a transformational technology, that almost nothing else will matter.