Wearing my altruistic tin-foil-hat, I would argue that Apple wanted to pay indie artists all along (because it's art and they respect them!), but were afraid of the antitrust implications of doing that (re: ebooks litigation). So they made this deal (of not paying artists) to go public, knowing it will 'backfire' and Apple would have the grounds to 'reverse' their decision and pay artists.
swift has a lot of influence on her fans. It's not a minor threat that apple is facing.