I will look here at two aspects of Diamond's response to Yali's question.
First, on the largest scale, I was surprised when I first read this book by the fact that he argues that culture had essentially nothing to do with which societies became powerful and which did not. I grew up reading books that emphasized the importance of culture. For example, in college I read Max Weber's argument about how the Protestant work ethic caused Protestant countries to be stronger economically than any others. Therefore, to read a book that argued that culture had no impact was surprising.
Second, on the smaller scale, I was surprised and intrigued by Diamond's argument that the fragmented nature of Europe's geography and politics helped to make it stronger than places like, for example, China. I had never considered the idea that having lots of relatively small countries would allow for more progress than having one large empire as in China.