In his terrific book, Private Truths, Public Lies:The Social Consequences of Preference Falsification, Timur Kuran writes about the phenomenon he calls “preference falsification”: People tend to hide unpopular views to avoid ostracism or punishment; they stop hiding them when they feel safe.
This can produce rapid change: In totalitarian societies like the old Soviet Union, the police and propaganda organizations do their best to enforce preference falsification. Such regimes have little legitimacy, but they spend a lot of effort making sure that citizens don't realize the extent to which their fellow-citizens dislike the regime. If the secret police and the censors are doing their job, 99% of the populace can hate the regime and be ready to revolt against it — but no revolt will occur because no one realizes that everyone else feels the same way.
This works until something breaks the spell and the discontented realize that their feelings are widely shared, at which point the collapse of the regime may seem very sudden to outside observers — or even to the citizens themselves. Kuran calls this sudden change a “preference cascade,” and I wonder if that’s not what’s happening here.