
More seriously though, cognitive behavioural theory argues that thoughts, feelings, and behaviours reinforce one another. You may have heard the term "cognitive dissonance" when it had its time in the limelight as the buzzword du jour; that's the discomfort that happens when two of those things aren't in alignment. Changing behaviour is hard, so most folks will naturally take the path of least resistance and just begin to believe differently.
We exist in an alienating system that requires unnatural behaviour in order to survive it (e.g., working a meaningless job for a wage). This is where we get the "you claim to hate capitalism, yet you participate in it- curious..." bullshit. It comes from people who can't stand that dissonance and so have defaulted to convincing themselves that capitalism must be good. The majority of people, however, don't even get that far. Even the idea of changing one's behaviour - especially behaviours practically required to survive an inherently fucked system - is off-putting. "Those who do not move, do not notice their chains."
Like others described, it's a combination of factors like learned helplessness, self-delusion, willful ignorance, and ofc the systems of propaganda/indoctrination that reinforce it. And of course, "It is no measure of health to be well adjusted to a profoundly sick society." Yet the folks responsible for defining pathology are entrenched in the system(s) responsible in the first place.
Side note, psychopathology is largely a weapon wielded against the proletariat, and I think we should consider not legitimizing the tools of our oppressors