I agree with all of the points (reasons) mentioned above and I'd like to add one simpler: the laziness. Because:
1. The mental health is a must. But even 100% happy, stable emotionally and so on (sane) guys may be too lazy to start something. An easy (for understanding) example -- all those Chads (and Stacies) who were initially without any psychological issues and they had got it all (it's a general expression meaning all the things life has to offer: good family, money, education, safe environment, health, love, etc.), but they were lazy and stopped the useful actions (to do sports, to eat healthily, to learn more) and years later you see a former 9/10 Chad already looks like some fat dadbod shaped Norman (normie) who isn't even enough educated and his overall rating is not more than 4.5/10. Or a former 10/10 Giga-Stacy who is now over obese and low educated and even the most needy incels are rating her as a "landwhale", i. e. not going to perceive her more than 2/10.
Why this happens? Because of mental health or because of poverty? Not at all, it's because of their laziness (lazy to learn, lazy to do sports, lazy to count calories, lazy to go shopping for healthier food, lazy to cook it, etc.)
2. Now, thinking about it, compare: if 9/10 or 10/10 people may minn (self-destroy) their looks, status, etc. just because they were lazy, what happens with all those incels (0/10 - 3/10)? (I don't even include the 3.5/10 - 4/10 nearcels and Normans.) If you're a 3/10 incel, for example, and you prefer to "face dysphoria" and only to face it, doing nothing about then the situation will become worse and later you will be probably 0.5/10 truecel.
3. So, to conclude it, the ascending (a.k.a. ascension) requires good mindset and some other factors (for example, being free, not being too stupid, etc.) but all those (factors) are useless if you're not doing, trying, acting, i. e. if you're lazy.