There are only three groups of people who could be subject to betrayal here: employees, investors, and customers. Clearly they did not betray employees or investors, since they largely sided with Sam. As for customers, that's harder to gauge -- did people sign up for ChatGPT with the explicit expectation that the research would be "open"?
The founding charter said one thing, but the majority of the company and investors went in a different direction. That's not a betrayal, but a pivot.