Then they [those who entered after V-II] should have known more about what they were getting into.
18 year old girls in the 1940s and the 1950s make for a good definition of naievety. Did they know what they were getting in for (what they were joining, and why)? Well, yes and no. Yes, they knew what existed at the time they joined. 15 to 25 years later, the world around them was going through a massive whip-snap unlike anything in the history of the world before. As most nuns were not in contemplative orders, most were out in the world doing something - nursing, teaching, etc. and were just about as exposed as those around them who were not professed.
In addition, many of them were not overly sophisiticated in terms of their training; they were not studying to be priests, and so they did not necessarily have a grasp on religion much above a high school level unless they went to college; and that was no guarantee they would learn a lot of theology. Religion perhaps, but not theology.
And suddenly, without a whole lot of direction, they had directives coming down from Rome, without much of anything in the way of preparation or specific rules as to how they were to approach the issues. And not unlike a child that has been strictly regimented at home and then suddenly one day finds themself at a college far away, and with no one to write or enforce any rules, they reacted in a similar fashion - there was a mental, emotional responce of going from repression to absolute unfettered freedom and common sense, if any existed, was lost.
Keep in mind that the mindset prior to and during Vatican 2 was that there was the world as it is - that is, they lived in community with little or no personal freedom. They freely gave that up - yes, at age 18, when often there had been no personal freedom to begin with - but joining a convent and becoming 21, or 25, or 32 does not mean that one has shouldered personal responsibilites for one’s total decisions. The convent - through their superiors - determined when they got up, where they went, what they ate, how they dressed, what job(s) or professions they might be involved in; when they prayed, when they went to bed. And suddenly, it appeared they could have some personal freedom in making what Rome intended to be somewhat staid, carefully thought out gradual changes.
Only it wasn’t gradual, and it wasn’t staid.
They were further caught up in a world that was going through a radical secularized revision of what it meant to be a woman. That had nothing whatsoever to do with V2; it was simply what was going on in society at the same time. The net result was that Rome, by directing them to review, for example, their habits (some of which were literally dangerous, e.g. in driving or next to impossible to enter a fehicle while wearing), habits that went back multiple centuries in some instances; and by directing them to review their charism, without providing a specific process, gave them what appeared to be total, unfettered discretion to change at a time that secular society was going through radical changes. It was the effective equivalent of throwing gasoline on a raging fire and the backdraft caught almost everyone.
It also helps to keep in mind that one underlying presumption appears to be that those who joined convents did so for solid, valid reasons. Some did, and in fact many may have; but it would be the height of ignorance to presume that all did.