Did they? I admit i'm not super well-versed on the matter, but I never heard anything about AMD helping to create OpenGL. Silicon Graphics are the company who are generally credited with developing OGL.
AMD seemed to be focused primarily on CPUs prior to their acquisition of ATI in 2006. Probably a good business move for AMD, but there are people who would say it kind of ruined Radeon. I can't disagree either. I don't play brand loyalty and value healthy competition, but for a long time now Radeon cards have been a pain due to poor drivers. OpenGL in particular. I ended up just buying an Nvidia GPU after being fed up. Hopefully someday AMD will fix their shit OGL drivers, but i'm not holding out hope. I'd guess AMD are probably doing well enough with sales from bitcoin miners who buy them for non-gaming purposes.
Dolphin, PCSX2 and Cemu are often swamped with complaints from AMD users with various glitches, instability or performance problems that aren't nearly as prevalent on Nvidia cards. I assume the same is true of Citra. It's a huge relief to many whenever Vulkan is made available on these emulators, it allows AMD users to bypass some of the problems with OGL.