Functionalism argues that is the main cause of social change; conflict theory argues that is the main cause of social change

Deviant behavior is the root cause of change. The group liking stability have to alter to accommodate those deviating.

Conflict theory would argue WAR is the main cause of change. That's just my opinion. Changes in society is a Marxian Theory which states that when there is an uneven distribution of wealth, conflict results when the have nots try to take it from those who have. I abbreviated all of that into war because war is the ultimate conflict.