I'm not sure that the returns to direct participants in many revolutions have been net-positive (relative to a probability weighted sum of possible non-revolutionary outcomes), even many decades out. Certainly the initial pain that accompanies a revolution will dull, but that's a quite different. At the very least, the accounting becomes difficult enough that a rational-choice theory of revolutions begins to look implausible, unless we modify the theory to assume that young participants are irrationally overconfident that the revolution is going to go well. Consider the fairly small long term gains of fighter in the American Revolution, relative to a trend that favored the demands of the colonies anyway. Or the Russian Revolution, where the removal of the Czar was inevitable, but where fighting for the more revolutionary path afterwards was a terrible mistake. And also don't forget the large number of thwarted revolutions.

I don't think this quite flies. There's no particular reason to look for adaptations relating to national politics; that's a scale we didn't evolve to handle. (Interpersonal politics, sure, but young people aren't known for playing long games there.) And putting this down to explicit planning doesn't work either; we generally see shorter planning horizons among young people, e.g. in domains like finance, where we'd normally expect analogous arguments to apply. However, a youth bulge does seem to be correlated with social unrest. So, what's going on there? I'm not totally sure, but I'd start by looking at risk tolerance.