According to Guns, Germs, and Steel, why
The answer to this can be found on the last page of Chapter 15. This is p. 321 in the paperback edition of the book. The most important word in the question is “create.” That is the word we must pay attention to. Diamond says that the Europeans did not “create” an advanced society in Australia. Instead, they created it somewhere else and simply brought it to Australia.
The point Diamond is trying to make is that we should not criticize the Aboriginal Australians or think that they were terribly backwards. Europeans, he says, could not have created an advanced civilization if they had been indigenous to Australia either. Diamond points out that everything that the Europeans used to make their society had to be imported. Australia did not have native crops that they could grow. It did not have native animals that they could domesticate. Therefore, it was not possible for anyone to create an advanced society in Australia. Australia simply did not have the geography to allow that to happen.
Thus, as Diamond says
Europeans have never learned to survive in Australia… without their inherited Eurasian technology.
In short, they imported their society rather than creating it in Australia.