A lot of businesses do this. It's far less risky to copy a successful model than it is to explore the unknown space of products/services and find out what a successful model is, what to price it at, etc.
This is part of the reason systems like the patent system were created for inventions: to encourage people to bother exploring risky unknown spaces to develop inventions by granting them essentially a short term monopoly to harvest their reward which they would then compete against after a time period so society could further benefit from their finding by allowing competition to drive prices down and iterate on those inventions.
Obviously the patent system doesn't really serve this purpose anymore like so many systems that have been sidestepped/bypassed, changed through regulatory capture and corrupted by pure profit seeking behaviors.
It's a little bit different because Amazon claims to be a marketplace at the same time as curating its own specific product offering. It would be kind of like if a mall required all transactions from independent stores in the mall to go thru the malls servers and then the mall started its own product lines to sell based on that data.
That amazon does has been common knowledge since Amazon Basics first appeared. Obviously, Amazon is enjoying the enviable position enjoying being the mall, the payment processor, and everything else.
Many Amazon sellers only sell on Amazon, or have a large majority of their business sales there. This is equivalent to having insight to almost your entire business.
Most brands at Walmart and other stores are sold many other places.
There are many businesses who are 100% dependent on Amazon as a platform and Google as an acquisition stream. If you want to break out and sell on your own online platform, you're still dependent on Google, be it through search or advertising.
I would love to hear of consumer facing (B2C) online businesses who are successfully operating without any Google or Amazon dependencies to see if it's even possible in the current online ecosystem.
My hypothesis is that it isn't, and as such Amazon and Google should be broken up. They have close to a functional monopoly on consumers, but I'm putting forward that they also have a functional monopoly on online businesses in commerce.
Which goes back to the buyer problem, that they don't consider other channels. Then you get hostile co-development of browser extensions for cross-channel price comparison, and life in the jungle continues on as such...
