So the answer to how long it took the conventional wisdom to change in Nazi Germany is "too long." For strange as it may seem, the flesh often changes before the spirit. As applied to business, it implies that companies don't change. They go bankrupt. As applied to history, it suggests that dysfunctional regimes don't discover remorse and reform. They are simply defeated. Neither Nazi Germany nor imperial Japan experienced a change of heart. They experienced a radical change in circumstances.
The body got there before the soul.
Few in error see it coming. Or if they do, they act as if they don't. A careen toward a cliff is often ended by the physical fact of falling over the precipice. Gamblers, drinkers, debtors, and criminals of all stripes don't as a rule stop because the conventional wisdom has changed in their heads. They stop when they look around to see The End staring them in the face.
The way conventional wisdoms end is they are taken to their logical conclusions.
If the first-mover advantage belongs to the originators of the narrative, then an equally important role must be accorded the last movers. Their strategy is to remain the last man standing, and pick up the pieces. The last movers don't argue; they survive. They don't have to worry about the nonsense low-information voters believe because that entire system of cues will crash, and therefore the LIVs will be blank slates ready to be overwritten.
One often thinks of arguments as being settled by debate, via a kind of dialectic. Yet in fact arguments are often decided by survival. The narrative that wins in history isn't the most beautiful meme; often just the one that can show up tomorrow. One interesting example of this strategy is Palestine, and similar nationalisms. Their power is based on repeatedly saying "no" to anything and everything except their maximum demands. The Israelis think that reason is important. The Palestinians know that reason is unimportant. It is far more decisive to be the last mover.
Even on the global scale this has surprising implications. The United States after World War Two probably dominated the world simply by being the last mover in that conflict. There was a whole slew of pre-existing conventional wisdoms -- like colonialism -- which became irrelevant because they were consumed in the cataclysm. This insight has not wholly been lost. One way to think about China and Russia's grand strategy is that each aspires to be the last mover in a world without America.
The practical implication of this in politics is that success often depends less on persuasion than on assured survival. One of the first modern figures to realize this was James Michael Curley, four-time mayor of Boston. He had no interest in persuading the voters that he was an honest, upstanding politician. He simply set about turning Boston "into a city that would elect him." He packed it with the Irish constituents, in the process destroying the municipal economy. But though he ruined Boston, he was re-elected as often as he wanted.
Just as the power of conventional wisdom was never in the truth of its precepts, the destruction of established memes is not always a function of rational rebuttal. Myths are compounded of some truth, but are mostly held together by human ingenuity. Their job is to create cues; to illuminate the path of the LIVs.
The real function of knowledge is to enable survival. The function of narratives is to create a mental universe for the LIVs.