Amazon.com has the books in print catalog online, same as any book retailer.
It’s not as if all of that “stuff” is in their warehouse. Any good retailer can order it from the distributor.
Amazon became the “klenex” brand name of it. Same as Google. Others offering the same service.
But merely launching a website doesn’t mean that people will use it or that it will continue to be strong, especially in a market of similar competitors. Friendster was beaten by Myspace was beaten by Facebook. The “cool kids” determine where the people will “be”. And they left Myspace in about a year’s time after “Faux NewsCorp” bought them. They hate Facebook too now but haven’t decided where to go yet.
Alibaba has more sales than amazon and ebay combined. They’ve clearly done more than just “launch a website”.
There’s competition in every industry. Ask Polaroid. Ask Studebaker. Ask Wang.