In this case, the thing that made Amazon so great, before Prime existed, was that it had the "Things you might also like" section.
AFAIK it was one of the first online stores that used machine learning to recommend new and related items you didn't realize you wanted and to have user ratings for each item.
It was especially powerful for books/movies/music just due to the sheer volume of different titles that makes it hard to find new content you might like.
There are a lot of retailers that had the logistics and infrastructure for online sales, but the kind of marketing that Amazon did for up-selling was wholly new and something that could only be done online. So even if Sears could do it, it wasn't obvious back then to anyone that they should do it or how to do it.
Even now, the Walmart and Target web stores recommendations are just ok compared to Amazon. Even eBay seems less comprehensive in its recommendations.