One rule of thumb you very often get to see about planning and running a game and also writing stories, is that the characters should be “acting instead of just reacting”. But I think except for special cases in which the PCs are trying to establish a domain or something like that, this is not really a good way to describe the issue.
In virtually all cases, every story, both fiction and academic history, is about dealing with an extraordinary situation and returning things back to normal. What is considered “normal” depends entirely on the perspective of the people who are in the center of story. If you have a society in which group A keeps group B in slavery, and has done so for generations, the state of slavery would be the “normal” state of things for people who side with group A. But for those who are siding with group B, the situation would still be extraordinary. It just has been that way for 200 years. But when someone does start getting active in any way, to end the state of slavery, from his perspective it will be all about turning things back to what he considers normal. It does not matter if the extraordinary situation began 5 minutes ago or has been going on for centuries. Any character who feels he has to change things or stop an ongoing crisis does so because someone else, at some point, upset the normal state of things.