I'd read somewhere that the downfall of fascism is always on the battlefield. Fascism simultaneously requires that a large population believe they are a persecuted group in danger of extinction (else there's no reason to subjugate one's individual will & liberty to a strong leader) and that they are superior to those who oppose them (else their cause is futile and they ought to ally themselves with the superior force). The distortions in reality needed to justify these contradictory beliefs filter up into the leaders' decision-making itself, such that they eventually make stupid decisions like bombing Pearl Harbor or opening a second front in the European war.

Personally I think it is more 'they ensure they will get attacked and bite off more than they can chew'. Since the fundamentals of totalitarianism just plain aren't sustainable. I mean Hitler's economy was a conquest dependent mess and the Soviet Union ended up collapsing under its own weight.

As for ending up attacking each other I think that is a general authoritarian thing with purging to take/secure power - it happens with communism and it happened with monarchies.

One interesting outlier along the lines was Fascist Spain. It was caused by a chain of events caused by internal attack of fascists for their own cynical reasons. [https://en.wikipedia.org/wiki/Assassination_of_Luis_Carrero_...] Combined with a secret liberal king, Juan Carlos and the power was used to restore democracy.

soviet collapse was not so simple as just economic “overweightness” as much as gorbachevs “liberalizations” causing the whole thing to spin out of control: https://en.m.wikipedia.org/wiki/Dissolution_of_the_Soviet_Un...

>I mean Hitler's economy was a conquest dependent mess

No it wasn't. The economic recovery occurred way before the war did.