By 2007/2008 there was a trend in HPC research called GPGPU. This involved havky techniques to get the shaders to do the computations you wanted.
CUDA started appearing in 2008 with a framework (compiler, debugger) to do GPGPU in a proper way. It got the monopoly. They’ve been benefiting from first movers advantage ever since.
GPGPU was a thing well before that! In 2004, it was ready covered in a few chapters of GPU Gems 1, increasing to 18 chapters of the 2005 GPU Gems 2, which including an FFT implementation.
