AMD first started with open source graphics with the radeon kernel module and pre-SI drivers around ~2009. It was just that Mesa in 2010 was nascent and tiny with it only reaching OpenGL 3.0 support in 2012. It was less AMDGPU being a big deal in 2016 and more that was when Mesa hit approximate parity with the latest OpenGL.
> It was just that Mesa in 2010 was nascent and tiny with it only reaching OpenGL 3.0 support in 2012.
Which meant that people who wanted to play games were stuck with the proprietary fglrx and all the compatibility and other problems that come with a proprietary driver on Linux.
The big advance of AMDGPU was that it was a usable open source driver that made it into the kernel tree, which meant that kernel changes would no longer break the driver people were actually using because drivers in the kernel tree get patched when the kernel changes.
