Very few people understand just how sheer an impact curtailing female hypergamy as well as restricting the male tendency towards polygyny can have on the productivity and power of of a civilisation. Institutionalised monogamy, the most common way of achieving these two objectives
gives almost every single man a stake in his community and pushes him to work harder, fight harder, and be a more responsible citizen overall. It's no wonder than that it was the greco-romans with their institutionalised monogamy who ruled over swathes of gallic & germanic lands
and not the other way round. Even modern day studies show that married men are much more productive than any other group in the workplace. One such study from the US showed that at the peak of their careers, married men make $80,000 annually, while others average just $50,000.
Simply put, institutionalised monogamy is like a civilisational cheatcode to maximise the loyalty and productivity of the male members of society. Societies which are able to do this will almost always have an edge over societies where much of the male population does not have a
stake. Once you allow female hypergamous tendencies to destroy the institution of monogamous marriage, like in Western countries, you start to see its many ramifications: millions of men drop out of the workforce, many hundreds of thousands start to kill themselves, the society
loses its appetite for expansion and military engagements abroad, etc etc. Overall, a certain degree of 'sexual socialism' is required for any society to be successful in the long term.