They built cuda and embedded it as a foundational technology through university partnerships and generally paying attention to developers. Wrote documentation,

They built cuda and embedded it as a foundational technology through university partnerships and generally paying attention to developers. Wrote documentation, talked about their tech a lot, generally made the onboarding broadly work. They then had the good fortune that their competitors tried to leverage open source and cross company collaboration. While misc open source winning is sometimes thing, the industry built all their stuff on cuda instead of opencl or openmp. Nvidia thus built their gold mine. I don't think it's impenetrable. There are some design mistakes baked into their system that are going to be difficult to unravel without breaking backwards compatibility.