CAD IS THE REASON LINUX GAMING DOES NOT EXIST.
Absolute nonsense. CAD is the engine that kept OpenGL going through the years of vicious attacks by Microsoft. Even though Microsoft achieved near absolute victory in the gaming space and played an instrumental role in bringing SGI to its knees, it failed to kill OpenGL entirely, in large part because of the entrenched high end CAD market. While most CAD vendors did port their systems from Unix to Windows in the late 90's, they had little interest in porting to Direct3D. Microsoft was therefore prevented from undermining OpenGL on Windows by their usual techniques such as playing games with the driver APIs. During this period, Linux took over Hollywood's render farms from Unix, and that was another base of support for OpenGL, but it might not have been sufficient if Microsoft had ever succeeded in dislodging the tenacious grip of OpenGL on Windows-based CAD. And then there was John Carmack's famous refusal to switch to Direct3D, but that came close to the brink. Not any more.
In my opinion, the greatest threat to OpenGL ever was the noisy faction of game developers pushing for a complete break with compatibility for OpenGL 3.0 (I doubt very much that John Carmack was ever one of those, despite his well founded criticisms). In retrospect it was proved that OpenGL could achieve parity with Direct3D and more, without breaking compatibility. And now OpenGL basically owns the entire gaming universe except for the steadily shrinking part over which Microsoft is able to exercise monopoly control.
Well, and Linux gaming does exist, just not at the level where we can throw away our consoles quite yet. But that day is coming.
One can fairly ask, why is the Linux game market, with millions of potential customers, not already well served by the likes of EA and Activision? I don't know the answer to that, and I don't think you do either. It very definitely has nothing to do with the influence of CAD vendors on OpenGL. I tend to suspect the hidden hand of Microsoft, however I do not have firm evidence of that. And furthermore I don't care, because it is the very failure of the big publishers to serve the Linux market that has accelerated the rise of a vibrant and rapidly growing community of free and open content developers on Linux. I sincerely hope the big publishers continue to keep their heads up their proverbial colons forever, because it does our community nothing but good in the long run.