DirectX 12 isn't just much more like Vulkan, it's so shockingly similar, it's basically Vulkan. It's jarring when you read it for the first time because you ask yourself why it even exists, but a second later, you realize it's so Microsoft can own their own graphics interface, too.

I could be remembering this incorrectly, but that's the impression I remember.

DX12 was over 2 years old by the time Vulkan was released. People in the industry also use DirectX extensively and have for decades (Vulkan is fairly marginal in comparison); many modern graphics API features (mesh shaders, ray tracing) were designed and developed in DirectX, as Microsoft worked with closely with ISVs on these features before they spread to wider audiences and published specifications.

Honestly if you are creating games, with the rise of Proton and vkd3d, there is seemingly less need to target Vulkan today than ever before. Just target x86_64 Windows with DirectX11 or DirectX12 and you will even get Linux support (and some day, probably macOS) "for free". That's just for games, though.

Vulkan existed before with AMD's Mantle or whatever was called.

Nope, thanks to AMD giving Mantle to Khronos, Vulkan actually happened, otherwise there would be no Vulkan now, they would still be arguing about OpenGL vNext on those committee meetings.

There's that small thing of DirectX 12 predating Vulkan (and massively predating the useful Vulkan specs).

They look similar because both D3D12 and Vulkan have been 'influenced' by Mantle (Vulkan more strongly than D3D12 though).

Vulkan was released after both Metal and D3D12 btw.

And only exists in first place because AMD offered Mantle to Khronos, otherwise they would probably be discussing how OpenGL vNext would look like to this day.

While flohofwoe certainly knows this, for the others,

"Khronos is free to take as many pages as it wants out of the Mantle playbook, and AMD will impose no restrictions, nor will it charge any licensing fees."

-- https://www.phoronix.com/news/MTc2Mzc