Someone I know spent a fair amount of time around Habermas. Talking about the great man's lectures he has come pretty close to saying "it was mostly incomprehensible but clearly brilliant".
The acolytes seem largely driven by some sort of Messiah thirst. Once they commit to their charlatan god natural psychological defense mechanisms against admitting such a huge mistake kick in. And so they are willing to follow him off whatever cliff or, more appropriately, into whatever fog.
I would also guess that, for some fraction at least, the motives are (or become) largely mercenary, i.e., they derive stature, influence, and income from their status as the chief courtiers and thus have no incentive to expose the emperor with no clothes.
The phonomenon obviously afflicts mostly the humanities. Unlike in science, there you can play word games and construct elaborate theories with no fear of being contradicted since the theories are unfalsifiable by design [or, better yet, so slippery that they can mean pretty much anything the guru says they mean].