Comment by flohofwoe

The same can also be said about D3D12, it is at least 'heavily inspired' by Mantle. In the end, not much of Mantle has survived in Vulkan either though. Mantle was a much cleaner API than Vulkan because it didn't have to cover so many GPU architectures as Vulkan (Mantle especially didn't have to care about supporting shitty mobile GPUs).