That same hierarchy is constantly backstabbing each other and will kill itself and have to go into hiding with only two allowed to exist at a time.
It seems that once they go to war, they get their act together pretty well. I mean, in a matter of a couple decades, the Empire managed to seize from 1/3 to 1/2 of the galaxy, pretty impressive. (Albeit, they had advantages over the Republic that should have let them destroy them, but that's not the point.) And the Rule of the Two won't happen for about 2700 years, so they've got some time methinks. It's the same reason that the Empire's citizens haven't said, "forget this, I hear Democracy is in season" and had a revolution.