Apple and Nvidia - What happened?

Apple historically has swayed between Nvidia and ATI/AMD for their GPUs. However, in recent years, it seems like Apple has altogether stopped purchasing GPUs from Nvidia.

Its gotten to the point where there has to be more to it than coincidence. Nvidia's Maxwell architecture, now two years old, delivered brilliant performance and great TDP, making it much better suited to computers like the 5K iMac than the offerings from ATI Apple used. Similarly, Nvidia are again kicking ATI's Polaris chips with their new Pascal stuff. Apple loves performance per watt (hello thinner and lighter enclosures), and Nvidia have been killing it in this domain.

I love Apple, but dear god please give us a machine that actually has a half decent GPU, especially on machines with 5K displays.