“Servant leaders”. Good scrum masters are committed to the scrum foundation and values, but remain flexible and open to opportunities for the team to improve their workflow
They do so as a team member, or collaborator, ideally not as someone in control
It is crucial, for scrum teams to be successful, that only one person sets priority. That person is the product owner.
The product owner must prioritize the work. This is probably their most important responsibility because conflicting priorities and unclear directions will not only reduce the effectiveness of the team, but also could break the important trust relationship that the business has with the development team.