But what if they can increase their profits faster, short term, by ignoring open source?

Apple and Nvidia could hardly be more different here. Apple is a consumer brand, with basically zero presence in data centers. Nvidia is the opposite. They do make GPUs for "consumers" but it's for a small niche of hardcore gamers and basically irrelevant compared to what they make for data centers. An "app store" model would never work there.

New leadership could still lock down nvidia hardware more.