I think there is a biological aspect to all of this too...
Statistically we do have have more female ancestors than male. Good looking men have always fathered more children with more women, and many men will die without having fathered any children.
Also women's perspective of male attractiveness tends to be very skewed in that women tend to rate more men as "below average". And so the truly below average get rated very harshly.
So I think it's fair to say that incels have always existed. The only difference now is that rather than these men being invisible, they congregate online and create very angry and bitter communities which occasionally attracts media coverage.
I think saying that "all these men need to do is improve their personalities" is missing the bigger picture. We do tend to treat people differently based on how they look. Plenty of people report that they notice they are treated better when they are slimmer, fitter, or notice changes in how they are treated as they get older or if they have a physical or learning disabilities.
Likewise, not all of these young men have the ability to become highly successful or socially enigmatic in order to become more attractive. A couple of other posters have mentioned that a lot of these young men appear to have autism. Which, if true, will also weaken their ability to succeed socially or professionally.
So I can very much believe that these young men probably have been treated poorly and experienced rejection by their peers and romantic interests. This could be enormously damaging to their development especially if such treatment starts early in life.
I don't think we can do anything to change this reality either, as women aren't about to change their selection criteria and I don't think society is going to stop judging and treating people differently by appearances.
The incel communities are toxic and hateful and it is instinctive to hate them back. But I try to have a bit of empathy for them. They are clearly struggling and you have to wonder what their life experiences to this point have been like to make them this way.