He is responsible to the letter of the law (has to pay them for their work, provide a physically safe environment, etc.). If you start looking into it you'll find he actually doesn't have much responsibility to begin with.

Musk turned into an idiot, or was one to begin with, but we don't limit people's right to do business based on their level of maturity (partly because maturity is subjective, partly because that would mean the world would immediately stop altogether)