The official line in the Charedi world on the Jewish “Enlightenment” is that it directly lead to the widespread abandonment of Judaism. Most every Jew was serious. Then, all of a sudden, everyone jumped ship as fast as they could. Anything but Judaism; Zion, 10 brands of socialism, assimilation, etc.
The deterioration in Jewish observance before WWII was exponential, as explained in the posthumous book from Rabbi Avigdor Miller, A Divine Madness. This is because science and other knowledge are inherently dangerous, goes the claim.
Now aside from the scariness of the thought itself, this does not seem to fit with what we know about history. The time of the Rishonim is somehow considered inadmissible. And I forget the details, but there was a renaissance in medicine and philosophy right after the Spanish Inquisition, yet it only brought about greater religious devotion. So what was so bad about the “Haskala”?
As I understand, the real problem was how community leaders (Parnassim) and Rabbis dealt – or did not deal, with the earlier Cantonist decree that caused a massive “loss of faith” in the Torah leadership: What sort of shepherd abandons his flock?!
See here for more.