Open AI was always a pipeline for Musk. Use other people's donations to attract and identify the talent, then move them under his payroll.
I guess that's a win win for the employees and for Musk. Not sure how many other supporters Open AI has, though I doubt that's what they had in mind when they donated to support that effort.
Their mission, to add more open source tools to the ai space, is already being accomplished by for-profit companies like Google and Facebook.
If it weren't attached to Musk, and if Tesla never hired from them, I'd agree it's good to have a non-profit in the mix. As it is, if it looks and acts like a pipeline for talent, it's a pipeline for talent.
I don't think he ever intended to stay at OpenAI long to be honest. He was a founding scientist of the nonprofit, so think he went there to do his time before he found an interesting opportunity (either in academia because he just finished his PhD or in industry)