That's AI built by a very small group fooming to take over the world at 1%, going from a millionth or less of the rest of the world economy to much larger very quickly. That doesn't account for risk from AI built by large corporations or governments, Darwinian AI evolution destroying everything we value, AI arms race leading to war (and accidental screwups), etc. His AI (80% of which he says is brain emulations) x-risk estimate is higher. He says between 1% and 50%.