I was the second employee at Amazon. The first 3 of us discussed the goal of the company vis-a-vis physical bookstores many times during the first year. I was cynical about this stated intent, but it is true that even within the first few weeks of the site being open to the public, we were selling books to people without access to bookstores (or certainly without convenient access) - folks in the outback of Nebraska, US forces stationed overseas, people in Argentina.
That said, I think you can make a good argument that Amazon has, in fact, caused a decline in physical bookstores. As other commenters here have noted, it isn’t clear either way.
I trust that my source-ing is good enough for you?
