I don’t think any of them have done something unethical to earn their billion, but artist billionaires are certainly outliers.
They’re such outliers that it’s still a safe assumption someone has done something exploitative if they’re a billionaire.
Taylor Swift, perhaps? Paul McCartney. You only need one example to disprove the case.
It doesn’t seem ridiculous that if you make something and charge $10 and 100 million people pay you that you’re necessarily doing something unethical.