It's a blend of cognitive dissonance and confirmation bias. We can easily see the absurdity in a situation when it is being promoted by someone we are not associated with, yet we bend our reasoning into very odd shapes when we want to defend the absurd things that we have invested ourselves into.
I think it's more difficult today to get away with trying to memory-hole inconvenient facts about their past, but the WTS has no other choice if they want to keep the grift going. But they managed to make 1914 (as the date of the end, not the beginning of the end), 1918, 1925 and 1975 disappear. Making 1914 and the generation teaching go away will take some work- I think they made a big mistake trying to rehab it with the overlapping generations explanation. There have to be a lot of people who saw that as the last straw, or as the first crack in the foundation.