What's going on is not that complicated, but it's no less disturbing.
At some point self hatred becomes so utterly complete the individual stops desiring their own success. Even actively sabotaging themselves. They know they are shit and think they deserve to be punished for it. Unless you have the 'luck' to be born a socio/psychopath, that is the expected mental pattern. We are aware of all the ways we are shit even if we are not actively thinking of them, and we judge ourselves on it. If you don't at least put some level of effort in to bettering yourself, you will likely start finding ways to drag yourself down as a self inflicted punishment for your wrongs.