you got it backwards. east asia has been traditionally ploygamous, with men able to have multiple wives and concubines. all those nomadic asian tribes like Huns, Mongols, its top level men had harems. in China, polygamy was practiced until the 20th century after it got westernized.
polygamy actually degrade genetics. in such societies, ugly men can move up the ladder socio-economically and marry multiple foids. this ensures ugly genes to pass on.
polygamy is why noodle, sand, etc. are ugly compared to europeans. esepcially noodle, who have no face, no bod, with an ugly personality to match
while mongomy is actually eugenic.
Europeans are actually an oddity, in that they're very strictly monogamous. even kings (like Henry the 8th) couldnt just marry another woman, he had to divorce his current wife and when the Catholic church forbid it since there was no grounds , he got creative and broke away from Catholism.
mongomy ensured even top tier chads could only have acess to 1 foid. so the competiton among foids get huge, which end up making foids better looking coz now the sexual selection goes both ways. in polygamy, even ugly foids can just add to the harem of a guy and get to pass their ugly genes.