Why doesn't Chollet just make a challenge that reads like "Solve cancer", surely there is no solution in any books.

If the AI is really AGI it could presumably do it. But not even the whole human society can do it in one go, it's a slow iterative process of ideation and validation. Even though this is a life and death matter, we can't simply solve it.

This is why AGI won't look like we expect, it will be a continuation of how societies solve problems. Intelligence of a single AI in isolation is not comparable to that of societies of agents with diverse real world interactions.