Gauchat himself never asked why the liberals seem relatively impervious to change over time — they are today at about the same place as they were in 1974 — and why the liberals more resemble the uneducated conservatives and moderates in his cohort, who have also been relatively resistant to change. That is a mystery worth delving into.
This helps explain why. If you agree with the bad science you are more likely to cling to it and lose your healthy skepticism.
It may be relevant that in recent years there has been a number of well-publicized science frauds and much embarrassing politicization of science. One would expect better educated people to be more aware of these problems than less educated ones.
As for why liberals continue to believe, many of the frauds ( Diedrik Stapel comes to mind here) appeared to support their views (indeed, in many cases, that was precisely the point of the temptation for the fraudsters). So it may not be that much of a mystery.