A social environment consisting of an informal, vague group of people with a uniting interest; their sphere of activity; a subculture.
Political maneuvers or diplomacy between people, groups, or organizations, especially involving power, influence or conflict.
In particular politics doesn't just refer to the sort of things that affect government policy, but also has a sense referring to the gaining and losing of influence within a group. Think more high school than parliament, though there's plenty of the high-school type of politics involved in the other sort of politics, at every level.
So together it refers to the jockying for position, popularity contests, bitchiness, who-said-what-about-whom and so on occurring in the community that exist around "your favourite band".