Depends on the field. If you consider linguistics a humanities field (not everyone does), for example, that field’s academic job market didn’t actually properly crash until 2008ish, and that was pretty well unexpected by everyone in that field. (And on the non-humanities side, the academic job market in the life sciences had crashed by the mid-1990s, again to the surprise of lots of people in those fields.)
Also, there were a lot of humanities PhD faculty, not just students, who were blissfully unaware of how bad the job market was at that time—I know that when I entered my PhD program in the mid-1990s, there were still a lot of claims that a wave of faculty retirements were just a few years off, opening everything up for those of us in the pipeline.
Really, from reading the Chronicle of Higher Education regularly for most than 20 years, I’d say that it isn’t really until the last 10 to 12 years that people in academia have generally become properly aware that the academic job market is broken for the vast majority of fields. (And that’s actually probably the result of a generational shift, I think—it’s only relatively recently that there’s a critical mass of faculty who have experienced the academic job market as it now exists.) Even then, though, a lot of students entering PhD programs aren’t suitably warned about what they’ll be facing—and even those that are, well, you’re talking about the best and brightest, most of whom have had a pretty easy time with anything connected with college, and so of course they’re going to expect they’ll be successful, no matter the general odds, because they’ve always been successful no matter the general odds.
It’s a problem from all sides, really.