Amazon started out in 1994 as a pure online bookseller. What few people know, the first version of the online shop did not have an integrated search. Each article had to be accessed via the navigation. Amazon SEO was not relevant at the time.
The biggest challenge for Amazon in the past as well as now is to do justice to the customer. “Customer Obsession” or “Working backwards from the customer” are common phrases associated with founder Jeff Bezos. And so it was only a matter of time before the search function was implemented.
As it turned out later, about 99% of customers use the search and only 1% use the categories shown, but the topic of Amazon SEO only gains importance many years later.