DirectX 10, 11, and 12 all came out in the last 10 years. All had significant improvements over each previous one. MS has spent millions on making windows the high end gaming platform.
But in the 10 years before that, DirectX went from idea to version 9 (which was pretty good). Their PC game development almost stopped 10 years ago. Ever wonder where Age of Empires and Halo on Windows went? Xbox needed more resources.
This is very true. They've made some claims in the past about putting effort into PC gaming but now that the Xbox brand is struggling a bit vs. Sony maybe they're more serious about messing with the Windows PC platform.