> And, one single distribution channel (the amazon website) doesn't define a market (with almost zero exceptions, amazon's website not being one).

if amazon captures a large ratio of people buying goods online, i would certainly consider amazon itself a market. But unless they also control some other aspect of the online market, it would be hard to claim they're a monopoly tbh.

_Anyone_ can setup an e-commerce site and sell online. Amazon doesn't quite fully control the hosting, IP and backend servers completely!