Perhaps this link will help:
https://amazonpublishing.amazon.com/our-imprints.html
16 different Amazon Imprints: "Amazon Publishing is made up of the following imprints that publish books across genres and around the world."
Mind you, even "Indie" authors aren't what they used to be with Amazon's marketing efforts and Kindle Unlimited behind them. Individually an indie author is one thing...but "the Amazon indie market" is quite another.
All while publisher's CAN'T stop selling their books via Amazon.