Well, I mean, if we take what they themselves said (at the time) as truth, then that was their sincere mission:
> OpenAI is a non-profit artificial intelligence research company. Our goal is to advance digital intelligence in the way that is most likely to benefit humanity as a whole, unconstrained by a need to generate financial return. Since our research is free from financial obligations, we can better focus on a positive human impact.
https://openai.com/index/introducing-openai/
Of course, they could have been lying at that point, in order to gain interest I suppose , but they were pretty outspoken about that idea at least in the beginning.