Why it might succeed: the new orthodoxy is fundamentally self-contradictory. It is at once radically in favor of expanding state power (to achieve “social justice,” to “end racism,” to “enforce gender equality,” to “achieve socialism”), but at the same time radically opposed to the violent means by which state power is enforced (police and military), and radically opposed to the forces of unification that hold a nation together (e.g., patriotism, national symbols, common education). This means that they will expand state power to enforce their orthodoxy, even as they weaken the power of enforcement and the desire of the public to comply.
This is the first time that I am aware of in human history where this paradox has existed. Nationalism, Socialism, and militarism generally go together (as with Hitler, Stalin, and Mao), but they are fundamentally at odds in the new orthodoxy. Tribe-left is hostile to nationalism and militarism, but supportive of socialism.
The first attempt at secession (1861) didn’t succeed because Lincoln was at once wanting to expand state power to end slavery (a correct use of expanded state power to achieve social justice), but also willing to use the ultimate means of enforcement of state power (the military) and the symbols of nationalism (as in the Gettysburg Address) to achieve his goals. Our current tribe-left has no such consistency meaning they could fail where Lincoln succeeded.