Every organisation has it’s own politics and power dynamics. There are many reasons for this behaviour. We can’t state exactly what drives them to behave like this. But if your manager is at an influential or senior position and holds power, let the issue go unless it is a case of sexual or any other kind of harassment. Keep focusing on your work and Maintain a cordial professional relationship with them and everything will be okay.
We don’t like everyone at the workplace and similarly, everyone need not like us!