I'm sorry I disagree. WW1 and the Russian Revolution changed the status quo far more considerably than WW2 (In 1914 "the lights went out all over Europe", a whole way of life ended for ever). The bishops of the time saw no reason to reassess our relations with Protestants, Jews and atheists, the door was always open to them. There were no complaints from ordinary Catholics about the liturgy either.
After WW2 Pope John surprised the most of the Church by calling a Council, I was in Rome at the time and it was like a bombshell. Everyone was waiting for the next pope and expecting him to be Cardinal Siri who certainly would not have called a Council.
The defections came about not because people were conscience stricken but because they were lured away from the path of virtue by liberalism, consumerism and hedonism and the Church stopped preaching against such things. The same happened in Eastern Europe since the Wall came down and the modern Church still ignores it.