D3D11 is much easier to use and more reliable than OpenGL etc, using OpenGL would increase the cost to finish the game and no meaningful gain since Linux is essentially irrelevant.
Also most game devs don't have Linux machines to build or test the game on in the first place.
I thought about it once, tried installing Ubuntu-- it wasn't as simple as I'd like, but eventually worked.. except it didn't seem to be aware of the GPU and was running at 640x480 or some shit.. deleted it.
Swift is Apple garbage and there is no expectation it would run on anything outside of iOS.
Crystal not working on Windows indicates to me that are implemented the run time idiotically-- should have just reused the C and C++ run time & standard libs, as this would have given them portability from the get go.
Exposing Win API or .NET is unnecessary, just allow users to call into C code for that nonsense.