In my opinion, feminism is largely responsible for the incel phenomenon. Feminism has always been a social movement that sought to further women at the expense of men, and didn't take into account the natural balance that had been struck over thousands of years.

Before feminism, society was rationally structured: females acted as child-bearers and raisers and support for their husbands, and in return the husband took care of the more difficult and demanding work. Certain things were expected of men, and certain things were expected of women in return. Men had political power, but also a duty to protect and cherish their wives and children. This societal structure makes sense because females are naturally inclined to nurture, and males are naturally inclined to strive and compete.

That is where feminism comes in. Females saw their disadvantages, without recognizing their privileges, and decided to change society to better suit them. For one hundred years females have pushed to become the equals of men in all areas that they were not already advantaged in, without challenging any of the norms that benefited them. Take for example chivalry: it is very rare to hear a female complain about this "outdated patriarchal custom" because it directly benefits them.

The modern female has been inundated by propaganda about them being oppressed, and it has created a generation of females who are incredibly entitled. They do not want "average" or "acceptable", they want something better. This is where inceldom comes in. In the old days, females and men would be naturally paired off, whether by their fathers or by their own choice, and it was very rare for anybody to go unmarried. The liberalization of the sexual marketplace, one of feminism's main accomplishments, has ended those days. Now, females are seeking ever more attractive males, and this leaves a large percentage of the male population with no hope of finding a lifelong partner.

The combination of the newly expanded sexual marketplace and female entitlement are, in my opinion, what led to the modern phenomenon of the "herbivore men" and the incels.