Psychology of a nitpicker

Mar 2021
Somewhere in the world we know
What is the psyche of someone who frequently nit-picks at everything and everyone around them? I have a feeling Nitpickers find flaws in themselves too but whether that is obvious or not may vary on how they deal with their ego. Like (1) if they're insecure and also inconfident, they might find flaws in others but not express it in an obvious manner.(2) But if they are insecure and self-righteous, then they might find problems in others and and express it loud and clear, as well as find issues in themselves but not say it or say it rarely. In both cases I think nitpicking comes with some level of insecurity. Also another question, can a person (call them person A) be of case (2), what are the chances that person A uses their flaw-finding abilities to take control of the environment around them? Generally, where is their insecurity coming from?
Some light on this would be awesome, Thanks!