How it happened
This timeline diverges well before humanity ever emerged, changing about at the big bang. This diversion has nearly all Newtonian physics completely re-written in a way that makes most abiotic elements much larger, and most biotic elements becoming adapted to this. The exceptions to both of these include insects, gasses, plasmas, and electrons.
These changes resulted in most plants becoming much larger, sea creatures rarely ever going extinct, just more rare, and most other creatures becoming stronger, faster, or, in the case of a few primates, elephant and dolphin species, much smarter. The one exception is humans.
(all changes are added in puberty, and the normal ones are magnified) Males became stronger, faster, less "me-first-y" and larger.
Females became able (and usually did) to weigh many tons(and have measurements in yards) before gaining side effects other that lack of movement, became incredibly intelligent, and lost most physical strength.
How it worked out
These changes caused humans to live an ant-like life most of the time, building massive castles with throne rooms in which two or more women stayed, leading their city, while the men lived their lives and did as they were told when they were told, eventually splitting and growing into modern times, albeit with women leaders, and less problems, (with the exception of some massive cold wars and small scale man-to-man or man-group to man-group battles.)
As in our world, their are cultural differences, here are three examples.
America The Americans are known for three things- obesity (in this world that's men at 500 and women at 10,000), being mostly nudists, and entertainment. With having a constitution, being the only pace with nukes, and having about 2/3 of the land devoted to agriculture, America has become filled with MASSIVE women (getting into the 25,000 range), and men who spend most of their time playing, either on a computer or a console, or at a sport.
England 1600's fashion never went out of style, and women are pretty small on average, comparatively,(larger ones have been nearly 43,700, but mast are only 3,000.) The English spend their time trying to convert the world to the church of England, fending off the rest of Europe, watching and playing American-made games and movies.
Kuwait This place prizes fat in our world, a trend carried over into this one that obesity-related health problems, ones women aren't really able to get without absolutely MONSTEROUS proportions. Men here are slaves, and this country's only sports are force-feeding, board-snapping, (where a woman sits on a board, tied to it, and is fed until she gains enough weight to snap it,) and coffin-busting,(a woman is placed in a plastic box and fed until it explodes.) These people are at war with all their neighbors, and battle on only to gain more territory, because their belief about territory is the same as their belief about women.