(I'm considering this page a work in progress. More citations and such later, and I tend toward discursiveness anyway)
Plenty of people at various times have left their ideas about this before now, and I have always found it a totally fascinating idea. To tease enough small detail out of just the MM, PHB, & DMG to build a campaign environment that is somehow as "close to the bone" of the AD&D rulebooks as one could possibly create. I can't even sure that it would be a setting I would have much interest in playing in or running - but it is an interesting thought experiment that many of us have spent some time with.
These details range widely - from the implications of specific game rules (like Gold spent = experience points, the Cleric class almost certainly necessitating the presence of gods or god-like things & alignment, etc) to the spinning of fantastic causal chain constructions of the social reality of life in "D&D land" (DMG pg 106 the Humanoid Racial Preference Table, the selection of possible NPC personality features).
It rests on some fundamental/pseudo-fanatical SOPs like:
1. Pedantic, literal reading of minute detail and cataloging thereof. Sometimes a joy in itself - a very difficult endeavor to sustain (for me anyway).
2. An ability to focus mostly/only on details of fine granularity. Example - the assumption that magical artifacts exist in the first place vs what the presence of The Throne of the Gods implies, range and varieties of Men subtables in the Wilderness Encounter section (though Gygax has said that those were intended as "primitive examples" that DM's would certainly rework to fit their own campaigns. (Oh God! Am I going to have to find that one in the Enworld monstrosity? No!)
As an example, these are the points of interest I draw out of the first entry in the first AD&D book - Aerial Servant:
conjured by clerics
can be found roaming the astral and ethereal planes ("natives"?)
move twice as fast as the invisible stalker (suggestive of conjuration 'arms race' between clerics and magic users in the past?)
Scott's from Dragonsfoot (2006) --- I find this really inspiring.
Amazing "speculative analysis" by Scottsz of WG4
I spent some time using the Internet, trying find an attribution for the phrase "There is no such thing as discovery, only recognition or re-discovery" - but that is a paraphrase. Hence the difficulty of citation...