I don't think 'prognosticating an ant farm' is actually grammatically correct, because 'prognosticate' means to predict an event. And 'downmarket' is a rather strange, awkward term here; I wonder if the writer was a native speaker.
I would also say that 'oblivious,' at least in modern English, normally does not mean forgetful, as the etymology might lead you to suspect, but rather unaware, inattentive, uncaring, uninterested.
So I would assume here that 'acutely observant obliviousness' means something like observant of even the finest details, but completely unaware of their importance, utterly blind to any larger significance.
It makes me think of people with autistic disorders, who IIRC may be able to observe behaviors acutely, but (without remedial training) can ascribe no social meaning to them, because they simply don't know or care that people's actions mean anything. I think that's actually a very good description of orthodox theologies that placed more emphasis on the afterlife than the present.