I think you meant (in bold) "did
not know (though)".
I'm not satisfied with your analysis of NP1. It suggests that you did not know a depth of understanding, when what you didn't know was the possibility of understanding so deeply.
This is indeed a good one for tangles and snarls, isn't it?
You mean T.C. Mits? (The common man in the street?) Yes, native speakers make out the meaning of this and even more complicated structures intuitively and with great ease. Whether they could come up with the same paraphrase I came up with is beside the point. When you ask a centipede how he manages to walk with so many feet, he gets so tangled in his explanation that he can't even walk anymore. The same thing happens with native speakers who have no training in the analysis of language. It is possible to "know" without "knowing how", I suppose!