By psychoanalysis, I mean all the people talking about why he did this, what he was thinking, etc. Going on about his tweats and things he put in his books and treating them as "clues" is just one expression of that.
Hell, if there's one thing we do know it's that we didn't get to see _why in his early developing years. When he joined the community, he was already a bright, talented guy with an assortment of interests. It's harder to look at somebody and figure out what they were thinking if you've only ever seen them when they were fairly mature.
I can't even parse that...
EDIT: Oh, I could actually check your profile. Some people fill those out.
"Going on about <something>" is an idiom I've encountered in Texas and seems common throughout the Southeastern US as well. You can get the essential meaning by thinking of it as a shortening of "Going on at length about <something>" with strong implication of excessive length, though it can be (and often is) used to apply to whole discussions among multiple people.