The notion of ownership is different from what those of us who have purchased physical media tend to believe. We really don't own any of it - just the rights to consume it under certain restrictions.
Things can go very wrong - I have no idea what the specifics are in this case, but imagine if it was a mistake or a minor infraction that managed to piss off Amazon ... and Amazon doesn't hold the rights either - they are merely a sales conduit which happens to have to power to turn the consume/don't consume switch. (like Apple and a few others)
Fortunately my Apple music is DRM free, but that isn't the case with "my" books - Amazon or Apple.