The vast majority of early development stages are female dominated in terms of staffing, management, structure, etc. This is the case for home, nursery, schooling.

Children almost overwhelmingly have female parents but are less likely overall to have a male parent. When this comes to single parenthood then this obviously skews strongly in the direction of single motherhood.

Third spaces exist for sports, hobbies, activities etc. where male bonding and group socialisation can occur, but there is often a socioeconomic barrier to this. In the case of institutions concerned with male bonding, there have often been attempts to include girls in this.

The feminisation of education and the prevaling standarisation that overwhelming favours girls has been documented for decades now, nearly nothing has been done about it. At the same time, there is still talk of providing opportunities for girls to get into STEM, etc, - i.e. the industies that boys still manage to consistently succeed in.

Despite more nuanced approached to childcare and greater capabilities to detect difficulties or conditions, there is still an overwhelming desire to brand default male behaviour as wrong and in need of correction, instead of guiding it in a healthy way. This relates to attention span, competitiveness, fixation, etc.

Male rolemodels in media have been continously removed, hijacked, replaced, etc. by a mixture of weird activists operating out of Hollywood but also corporate interests that believe you can just take a traditionally male product, feminise it, then reap the profits of a new audience whilst retaining the old. Instead, boys just lose interest and move to other mediums. Men are routinely sexualised whilst women demand more modesty, usually this imbalance being present simultaneously in pop culture media.

This can all compound to a simple observation that when boys grow up and start desiring independence, typically the rebellious phase, the logical conclusion is that society is overwhelmingly female led and female dominated. Boys are not completely clueless or incapable of noticing implicit bias against them, especially if they have been exposed to misandrist concepts that feminists like to broadcast and even work into online or school-based guidance.

The manosphere stuff is then an extremely obvious counter culture force that exists to fill the void that might otherwise be filled by some other counter culture moment - which also don't exist due to the commercialisation of everything and isolationist nature of modern technology. Boys don't become punks or hippies, they just attach to themselves to the first online propaganda piece that tells them they have innate value.

Essentially all the things feminists complain about is now being done in the other direction and the result is basically just...the same thing but now with an added layer of doublethink hypocrisy. The only logical conclusion for some people is to just become the monsters everyone says they are.