Maybe Apple will stop the nonsense and support the Vulkan API, too.
So since somebody made a non-compatible clone a couple of years later, Apple should have ditched their work and lost the power to make decisions as they see fit in the process? That doesn't sound like something that would appeal to them.
Metal from 2014 had a lot of assumptions (for example, that the GPU shares memory with CPU), so it could be released earlier due to being simpler. That's why it was supported only on iOS.
And that's why there were more Metal releases and refinements. Apple had to make improvements to make it equal in its capabilities to Vulkan 1.0 and DX12.
In fact, Metal is powered in all iOS SDK too.
That's backwards — Apple contributed the Movie file format as the basis of the MPEG-4 file format.[1]
[1] https://en.wikipedia.org/wiki/MPEG-4_Part_14#History_of_MP4
They invested heavily in their own API (Metal) while OpenGL committee was sitting on its ass doing nothing, and released it a year before Vulkan was even announced.