What are some of the reasons political systems breakdown and lead to political revolutions?

Answer 1

There are many theories on why polities breakdown into revolutions. Some include:

1. Class struggle (historical materialism) - people exist is distinct 'classes' and these classes have different interests. When technology changes significantly, our relations also change and thus the old system is changed. When change is repressed, a revolution might begin.
2. Political violence - elites struggle for power over a polity (state) and will use revolution as a means to achieve mass popular support.
3. Relative deprivation - in conditions of economic downturns or high levels of wealth inequality, people feel a dissonance between what they consider 'rightfully theirs' and what they have. They correct this imbalance by resorting to revolution en masse.
4. State or military breakdown - polities often maintain their rule using force. When the ability to use force weakens, revolutions might start because people exploit their chances to change politics forcefully (as opposed to within the system).