Reddit mentions of People Styles at Work...And Beyond: Making Bad Relationships Good and Good Relationships Better

Scrum masters can come from any background. Having PM knowledge is helpful but not required. A scrum master is a guide and coach for the team. They are responsible for ensuring the team is following the rules of scrum, facilitating their meetings, and overall helping the team on the path to high performance.

Understanding the rules of scrum and the agile principles are more important. In your first SM role you will likely be following the scrum guide as closely as possible but the importance will be in understanding why the practices exist. What is important in the daily scrum? Why do we ask the 3 questions? What is the real goal in that meeting? etc... Eventually guiding and facilitating becomes more about the principles, outcomes, and goals than the rules of scrum but that comes with time.

Pay attention to the people on the team. I suggest looking into some personality or team-working books as a scrum master should be in tune enough to understand the work being done (technical and business purposes) and how the people work together. Conflicts amongst team members can be a difficult impediment to remove.