There was a significant gap between Amazon launch and having two-day shipping — it took years of behind the scenes development before orders started arriving notably faster than other retails. Sears' numbers include regular postal delivery in both directions so switching to online ordering would have cut them in half with no other changes (and don't forget the efficiency wins from orders arriving as validated electronic data rather than handwritten order forms).
The reason why Amazon was successful early on was selection and pricing. They had _everything_ rather than the generally limited selection most people had from local stores and the pricing, especially for things like technical books or genre publications, was often very favorable. Yes, some people lived in major cities with awesome bookstores but for most of us in suburbia the selection was what the local supermarket / drugstore carried or a non-trivial drive.
The reason why Amazon was successful early on was selection and pricing. They had _everything_ rather than the generally limited selection most people had from local stores and the pricing, especially for things like technical books or genre publications, was often very favorable. Yes, some people lived in major cities with awesome bookstores but for most of us in suburbia the selection was what the local supermarket / drugstore carried or a non-trivial drive.