The winning group splitting into left and right factions is almost a social physical law
When fighting over any scarce resource, if one group teams up and the other doesn’t, the first group tends to win. This is the fundamental reason humans tend to consolidate into two factions and fight each other over scarce resources until one faction wins. The winning team enjoys a brief honeymoon, after which it often divides into new left and right factions, and the battle begins again.
Everything changes when a frontier opens up. A new realm of unoccupied space means resources are suddenly less scarce. An aggrieved group can choose flight rather than fight. The would-be revolutionary doesn’t have to try to overthrow the ruling class anymore. Those who don’t like the current order can leave for the frontier.