That's not true.
The fact of the matter is Amazon had a huge lion's share of the market for e-books (measured by $$$). They had such a huge monopoly position that they could dictate terms to all publishers, more than once they refused to carry a publishers e-books (effectively killing them) if a publisher didn't agreed to some terms that Amazon wanted. They would stop selling PHYSICALS books to push the contract. Since no one else old e-books in any reasonable quantity, Amazon was in the monopsony position of being the only real buyer.
So not only did they do that, what they really like doing with selling Kindles. And a great way to sell Kindles is to discount the books below the actual selling price; eating the loss and making the publishers e-books on other platforms (as well as physical books) worth less. To a fair degree it didn't matter to Amazon if the prices were unsustainable, it fueled growth in their devices which fueled growth in their profits.
And then they would do something like push Prime since you could get free books that way (more loss for publishers) and Amazon would make up the money. And the publishers could either choose to go along with it and get a small price for each book or say no and get all their e-books pulled.
Plus Amazon had cable direct, which was a publishing platform that anyone could access. This meant that they had TONS of content by authors who were willing to sell it dirt cheap. This put the publishers in the same position that the media is right now competing with YouTube. And of course some of those books were actually really really good (Silo series by Howey) and became great sellers. Maybe even books that the publishers had passed on. It wasn't all garbage. So Amazon could show the publishers that they weren't nearly as necessary as the publishers thought they were.
Apple NEVER did anything like that. When Apple sold music it was at a flat price. They never undercut the publisher. After a little while to even let the publishers raise prices. And the whole time selling on the iTunes Music Store was an option since you could still sell CDs or sell to other DRM music stores like Amazon.
Amazon was easily the standard oil of the e-book market. They WERE the e-book market. No one ever went after them.
Then Apple came along, is part of the deal with publishers that broke Amazons monopoly, and they got an antitrust suit. None of that makes any sense to me.