So far the examples I've heard are: humans will ask AI to help humans solve human issues and the AI will say humans are the issue and therefore mystically destroy us somehow. Or, AI will be inherently interested in being the primary controller of earth and so destroy all humans. Or, AI will for reasons be inherently misaligned with human values. Andrej Karpathy Said it will fire nukes on us. Elon said pen is mightier than the sword and civil war is inevitable.

Because then you wouldn't be able to get this many people to sign the statement.

It's like with climate change, every serious scientist agrees it is a problem but they certainly don't agree on the best solution.

If the history of the climate change 'debate' is anything to go by this statement will do very little except be mocked by South Park.

It’s not on the same page as the signatories but they do have this: https://www.safe.ai/ai-risk