May I suggest human nature?
Any very large group of people, born into certain circumstances, will act pretty much the same way.
Lots of kids, lots of money, rapid technological advances, the seeming security of a traditional culture....trouble was coming, but society could not see it coming.
I remember our high school social studies teacher, a PhD and a socialist, saying to a group of high school students in 1969 that most of the girls would be married and have children by the time they were 25. Even highly educated people who wanted change could not imagine the change that was to come. It takes a lot of imagination to see the possible consequences of seemingly benign ideas.