Regarding societal evolution, one of the best examples is slavery. As societies evolve, slavery disappears. Previous studies have shown that in ego/ethno-centric cultures 15% practiced slavery and it was black on black, white on white and yellow on yellow. Race did not matter in those studies on indigenous populations and they practiced slavery because worldcentric morality had not yet emerged on a wide scale)—hence this unfreedom is not primarily due to the presence of an oppressive force but to the absence of a higher development. This is key to understanding the far-right today - they are not being deliberately oppressive - they lack the higher development needed to see they are oppressing others with their beliefs and subsequent actions.
Quoting Wilber "This evolutionary stage also meant that identity could expand from ethnocentric (“my-special-group” identity) to worldcentric (or “all-groups” or “all-humans” identity, which strove to treat all people—not just a special group but all people—fairly regardless of race, color, sex, or creed). This was a staggering shift in values—from ethnocentric group-centered to worldcentric all-humans centered—and for this reason, in a one-hundred year time period (roughly 1770-1870), slavery was outlawed in every single worldcentric modern-rational society on the face of the planet—the first time anywhere in human history that this had happened".
So, the ending of slavery in all modern and post-modern societies is an example of societal evolution reflecting a 100th Monkey type of result though the actual numbers to drive societal change are around 10%. The integral studies showed that, for example, the abolitionist movement in the US took place with only about 10% of the population at a world-centric view which is where slavery obsoletes itself - it is too obvious at 10% that slavery is wrong.
That is an example of a societal stage driven by a percentage of people at a personal stage of development. For background I quote Wilber again "People are not in any way born with green values; those values are rather the product of 5 or 6 major stages of human development, 1st-person perspective of red, to a 2nd-person perspective of amber, to a 3rd-person perspective of orange, to a 4th-person perspective of green, to a 5th-person perspective of early integral, to a 6th-person perspective of late integral, and higher. Each of these stages “transcends and includes” its predecessor."
To me, from an evolutionary question of "why is green or later turquoise an evolutionary improvement?" the answer seems to be that in a complex society of specialization, earth resource depletion, and interdependence that we currently have, these advanced stages become essential for species and planet survival. If the human race does not evolve to these higher stages, it could destroy the planet at worst, or maybe more likely just kill off 90% of its own population.
And, back to your question of why some stall at different stages (everyone has to go through all of them through their life), it appears to be complex with many factors contributing: intellectual capacity (a mentally disabled person is not going to progress at all which means on a spectrum of intelligence there are likely max levels one can achieve); education certainly plays a role in maximizing potential; personal drive and curiosity to know; personal practices (previous studies show that the single best practice to move people on the cusp from one to the next level is meditation); and then of course the supporting activities/systems to all these like diet, exercise, schools, health-care, etc which without you cannot achieve max intelligence, emotional control, sound thinking processes, etc. The meditation effect is particularly interesting because prayer is a form of meditation - so religious practices can play a positive role in moving people along if they don't get trapped by the dogma.
Now, back to green.............. "But this postmodern stage—Integral Meta-theory’s “green”—brought a 4th person perspective into significant existence, which had the capacity to reflect on—and critically analyze—these 3rd-person “global” productions, and this is where green postmodernism (so named because it came after, and reflected on, the products of modernism) decided that this rational-modern mentality had, in too many ways, veered off course in destructive and counter-productive ways. And thus the civil rights movement, the worldwide environmental movement (which became larger than any political party anywhere on the planet), personal and professional feminism, the sustainability movement (in business and elsewhere)—all of what I have called “the many gifts of green. And yet, in the course of that, driven largely (if often unknowingly) by arcane arguments in academia, the originally healthy pluralistic postmodernism increasingly became an extreme, overblown, self-contradictory, utterly dysfunctional relativism, which soon collapsed almost entirely into nihilism and narcissism. It’s the nature of the leading-edge stage that its values, although they are only directly embraced by the stage itself, nonetheless tend to permeate or seep through the culture at large. (For example, when the leading-edge was orange rational world-centric, whose world-centric or “all-humans-treated-equally” values inherently included an anti-slavery stance, the Civil War was fought in America in order to end slavery, and over a million white boys died in the fight to end black enslavement—and yet not much more than 10 percent of the population was actually at the orange stage—but that value had seeped throughout the culture of the North, and many were willing to die for it—as many were in the French and American revolutions, which marked an orange democratic overthrow of amber monarchy/aristocracy.)"
Where he talks about green falling back into nihilism and narcissism is when I reflect on the rabid attitudes of progressives manifesting as overbearing PC, taking up causes like stopping water bottling (just an example I see), the micro-aggression issues colleges have had to deal with where people find the least little thing to be offended by, etc are when Green veered off course. It got stuck in its own loop. Reds actually came up with what I thought was a ridiculous saying that "liberals eat their own young" which i only now understand. But, the progressives who lost emotional control did become so vicious I can see how someone could make that statement. Think about the vitriolic attacks on GMO's, energy producers, etc - on one level I agree those things are problematic but some of these people would blow up Monsanto, Exxon, and Chevron with no solution what to do next figured out. They substitute one wrong with a much greater wrong. And, some of these far-left activists will cut off their nose to spite their face because they see certain things as so wrong - they have lost perspective. That is the negative side of green that caused the backlash that ultimately was that little extra that pushed Trump over the top.
Sorry for probably giving you more than you asked but it all started to fit together and I just kept going