Psychopathy is shockingly common. Technically, only 5% of people are full-blown psychopaths, but like all brain disorders it’s a spectrum, and everyone falls somewhere on that spectrum. At least 30% of the population exhibits sub-diagnostic psychopathic traits, such as an indifference to lying or a lack of moral compunction.
What people don’t understand about psychopathy is that it presents as an indifference (or an unresponsiveness) to empirical and normative facts. That is why psychopaths just do whatever feels good (which might include tormenting others), why they might be obsessed with money or power other pleasure-oriented goals.