I guess they imagine that extremist regimes will provide them with that power, without taking a moment to think “oh, wait, the chances that I’ll be the one oppressing and not the one oppressed are miniscule” (and that’s setting all other moral things aside).

I’m pretty sure the ones oppressing and the regimes always have something in common (race most often, then wealth). Even if there is a slight chances the regime might turn against them, the minority and the rest will be the first to bear the brunt of the force which will be cheered on. And by the time the regime turns on them (unlikely), most will have had enough of a clue to prepare or escape.