“Maybe” sounds like armchair speculation without any basis in fact that ‘maybe’ does not enrich real world conversations.
Or maybe it actually does enrich the conversation by providing an alternative point of view to consider, unless you expect everyone to take your equally speculative claim that "this was good for Amazon, not for customers or writers or the industry" as the factual truth when there is no such factual basis presented.
Apple had brought value and Amazon felt sufficiently threatened. Possibly you did not follow that market at the time, but this suffocation of Apple books division was wholly driven by Amazon and its understandable fears.
Apple had brought a better product at a couple dollar markup, which the industry of writers and publishers welcomed. Customers jumped on board, and Amazon became hopping mad.
Apple was unwilling to compete on price. It's fine with me, but the alternative is not to fix the price so that you cannot get a cheaper deal from competitors, the alternative is to offer better value and let the consumers decide whether they value your offer enough to justify the higher price tag.
Furthermore, I don't see how Apple "brought a better product" when the vast majority of ebooks were basically the same, Apple's ebooks were and still are not available on any epaper ebook reader and iBooks being worse or better than e.g. the Kindle App is pretty debatable.
From this Amazon-driven fiasco and the fury from the industry and customers, all parties learned ... While the books division was essentially dead and gathering dust, Apple shifted focus back to music, delivered premium margins to this industry of writers, performers and producers ... But this time the whole eco-system rejected the attempt to object to these higher margins.
Resulting high competition from (rather than judicially applied restrictions on) the innovator has caused improved products and faster develop cycle times from all music delivery platform players (Apple, Spotify, Amazon). And thank goodness!
Learned what? A very big part of this "high competition" you praise is price, which is exactly what Apple sought to remove from the equation in the ebooks market by enforcing the same price everywhere. Following your reasoning, you should actually "thank goodness" the Apple deal was declared illegal since competitiveness apparently works much better without fixed prices (which should be obvious...).
Furthermore, under the model from Apple there was no such thing as higher margins except for Apple itself. Publishers and writers were earning more under the wholesale model from Amazon. This was confirmed by the publishers themselves as far as I remember. The whole deal was not an attempt of the publishers to earn more money, it was an attempt to keep the perceived value of books artificially high even if it actually meant lower revenues from ebooks.
As a side note, Spotify is accusing Apple of anticompetitive behavior, with an ongoing FTC investigation and a complaint filed to the EU antitrust commission, so at least one of the key actors of the eco-system feels Apple is misbehaving in the music industry too.