Bill is a grafter, a liar and rapist but he knows what works in politics. She doesn’t. Good thing she refused to listen to him.
Perhaps she became so accustomed to having everyone wait on her and suck up to her as the wife of a governor and then the wife of a President, that she thought she actually had power and commanded respect. It sounds like she was a total bully. I think her bullying behavior combined with her position as the wife of a powerful man created a feedback loop. The more she bullied and got away with it, the more power she thought she had. And the more power she thought she had, the more she felt free to indulge herself with bullying (and criminal behavior and breaking many rules of common courtesy).
Many people see themselves as better than they really are, and Hitlery just had an extreme case of that. And in her case it fed on itself and made her ever more nasty, spiteful, evil, and reviled.