And I can provide numerous examples: Portugal's colonial holdings (Guinea-Bissau, Angola, Mozambique) were unwound after the carnation revolution because the overseas wars were consuming 50% of the national budget while the Estado Novo at home was a corrupt, violent, authoritarian, corporatist state.
The Brits could not square a global empire while their countrymen were rationing food, etc. at home. That had to go as well.
Despite all the Cold War propaganda spread since the fall of the USSR, in 1991, the Soviet Union was still a first-rate military power, with 35k to 40k nuclear warheads and >150 divisions, totaling 3.4M troops. It could easily suppress any of those pro-democracy protests, and all the CIA's burrowing in the Sovbloc would come to nought.
But there was no longer anything worth fighting for. Even people within the Party infrastructure had come to admit that they'd been living for a lie, lying for a lie, killing for a lie-all that for a lie!
The Qing dynasty faced massive internal revolts (Taiping, Boxer), external invasions (Opium Wars), and technological stagnation. The empire resisted modernization too long, then tried too little, too late.
Overwhelmed by foreign powers and internal revolution (1911), it died because it could no longer defend the illusion of legitimacy.
In France's Ancien Regime, nobles were exempt from taxes while peasants starved; France had a bloated, corrupt court and massive debt (partly from helping America fight the British!), yet refused reforms.
Nazi Germany claimed to be defending “Western civilization” while practicing industrial genocide and totalitarian control over - wait for it - Europeans!
One contradiction doesn't bring down a political system, but it cascades, because a hypocritical system dives deeper into hypocrisy until it eventually collapses.
