1995 Ford Crown Victoria wheel stud

If the stud broke when being removed, either it was cross threaded or over tightened when it was installed. When removing the lug nut, they are doing nothing more than unscrewing a bolt. Therefore, what wrong did they do? The only thing I can think if is if they were tightening it rather than loostening it. But how can you prove that.

I wish I had a better answer, but it sounds like the last person which installed it may have caused the problem.