CUDA is a technology investment that gives Nvidia a moat, but there is nothing exclusionary about it, Nvidia invested in tooling years ago ... it will just take time for others to catch up.
NVDA banned CUDA translations layers, that's pretty exclusionary because it denies interoperability. There was already a discussion about it here: https://news.ycombinator.com/item?id=39592689
Well, they tried to legally prohibit it, but as people in that thread pointed out, it's legally irrelevant in most developed countries ... so another hardware maker can fund a (legally) independent team in say France (most favorable reverse engineering laws) to break it / copy it / do whatever they like ... and then open source the output for the rest of the world.
It's even dubiously legal in the US ... but there it would be a war of legal fund attrition and Nvidia has deep pockets.
Still - break it in France, give it away ... US laws go poof.
It's really just the ongoing development of the software ecosystem that gives them their moat ... but it's a good technical moat because they steer future dev and others play catch up.