Peasant uprisings have little chance of success when the governing élites are unified and the state is strong, Peter Turchin notes — but governing élites rarely stay unified, because everyone wants in:
The connection between population dynamics and instability is indirect, mediated by the long-term effects of population growth on social structures. One effect is the increasing number of aspirants for élite positions, resulting in rivalry and factionalism. Another consequence is persistent inflation, which causes a decline in real revenues and a developing fiscal crisis of the state. As these trends intensify, they result in state bankruptcy and a loss of military control; conflict among élite factions; and a combination of élite-mobilized and popular uprisings, leading to the breakdown of central authority.
The Law of Unintended Consequences is strong:
When the Assembly of Notables refused to approve a new land tax in 1787, they did not intend to start the French Revolution, in which many of them lost their heads. When Tony Blair was Britain’s prime minister, he set out to increase the proportion of youth getting higher education to 50%. He was presumably unaware that the overabundance of young people with advanced education preceded the political crises of the age of revolutions in Western Europe, in late Tokugawa Japan and in modern Iran and the Soviet Union.