What are the political causes of social conflict?

Northern Ireland and Netherlands both are predominantly Christian but divided between Catholics & Protestants. In Northern Ireland the Protestants have stayed richer than the Catholics. There class & religion overlap each other, Catholics have been poor & have suffered discrimination whereas in Netherlands class & religion tend to cross-cut each other and both are equally likely to be rich or poor. Social discrimination in Netherlands is not overlapped by economic issues. Both the Christian communities have equal number of rich and poor. It means they have conflict in Northern Ireland and it is not so in Netherlands.

Are overlapping social differences the only cause of social conflict?