If I was working for Open AI, or had donated or provided funding, I would probably be angry that Elon moved a great engineer to Tesla because he thought that was more important. I would wonder if we could truly build a great team of if SpaceX and Tesla would just poach anyone exceptional.
I would hope that exceptional individuals would work wherever they choose. In most cases the folks who stick with non-profits like that they're working for a non-profit, even though the financial rewards are smaller than industry.
People will generally go where they are paid the most, especially when choosing between two companies both working on very exciting AI projects such as Tesla and OpenAI. And Elon is setting (or at least influencing) what both companies are willing to offer him.
These are people, you can’t “steal” them.