Interesting - makes sense, thanks for the context.

I'd suspect part of the reason Nvidia went their own way is because their way is better? Is that the case - or is it more about just keeping things proprietary? Probably both?

If I had to guess, some mixture of ability to improve things faster with tighter integration at the expense of an open standard (pretty much what has generally happened across the industry in most domains).

Though this often leads to faster iteration and better products (at least in the short term, probably not long term).