Incels hasn't been about that in a long time. It's already evolved into "self-improvement" by adopting far-right extremist ideology. In particular that of being a hyper-masculine bigotted conservative man. Their underlying theory of world is still the same. Love is fake and women cheat and leave you taking all your money unless you become the strong man chad and dominate her. Instead of the pit of self loathing based on the premise that everyone is out to get you. You become the biggest alpha over every other guy. Fundamentally the ideology is the flip side of the same coin. It's a very dark misanthropic view of the world.
It's surely been some sort of cult brainwashing. Tear guys down with crab bucket mentality. Then build them up according to their doctrine.
Being physically healthy makes it much easier to be mentally/emotionally healthy, but they still don't just get better unless you actively work on them.