It manifests itself and is only possible wherever there is an imbalance in social power.
I think focusing on oppression alone is a distraction, because one reduces oppression to some moral failure of individuals—corrupt rulers, cruel kings, bad bosses, etc.
However, I think there is very good evidence that oppression is something that emerges systemically. It is a combination of human tendencies in particular institutional contexts, and it is these latter institutional contexts that need the focus—since we can do more about them.
The institutions themselves and the types of social relations they define promote particular values and norms. In this respect, institutions can become self-reinforcing, and patterns of human behaviours—such as the oppression and authoritarian relations we find undesirable—reproduce themselves.
For there to be less oppression, there also needs to be more egalitarian social relations, and institutions which will promote equitable and reciprocal social relations.
The Stanford prison experiment is a notable example of what I’m getting at. Although this is an extreme case, the same sort of authoritarian and oppressive patterns of behaviour can be found in more subtle forms in various other institutions—workplaces, family households, schools, etc.