Why did the empires that existed in Europe before the World War collapse?

1. National movements for independence against the background of a sluggish war led to the collapse of states and empires in Europe, just as the threat of the red terror and the fall of democracy led to the fall of empires.
2.Republican device
3. The Comintern was for the unification of all states into one communist state, the socialintern was for equality in rights, but within the limits of independent states.
4. The uprising and short-term absence of the ruler of the Hungarian government.