It's hard to believe that Tesla didn't become aware of this after a few months. Just like farmers who can't hire american people to pick their crop with backbreaking labor and low wages and who hides from hiring undocumented workers from mexico, they are morally responsible for treating the workers well.
US politicians should address this situation by working to eliminate b1 visa fraud. If it turns out not to be illegal to do this kind of job, we should change the laws to disallow it.