"Flat UI was super hot months before Apple has used it and that’s rarely happened before."
One problem is Apple's yearly release schedule. This allows other companies to innovate while Apple is still waiting months for their next scheduled release.
There were smartphones years before the iPhone, even ones with touchscreens and no keyboard. There were tablets decades before the iPad. There were online application market places years before the App Store. Apple doesn't often do anything first, they just do it 'right', and that means taking time and thinking it through.