To Bezos, a market controlled by a single large capital allocator is a free market. Unless the allocator is government of course (unless there's subsidies to apply for!).

The idea to me is strange; I shop on Amazon, but also dozens of other online websites. It's really not hard to buy from some place other than Amazon if you desire.

Many of the same effects that make it extremely hard to set up eg. competing social networks are not present for online shopping - There's plenty of shipping companies, so you can ship anywhere in the world without capital investment; You can set up an online shop and send it to anyone, you don't need to have a huge customer base to make money (relatively speaking, obviously you need customers)