Genetic makeup…could be the case…after all, the terrible genes of the erev rav have penetrated all of us and we never know when and how they will manifest. In some cases, they manifest as m.zochor, or abuse, and in other cases as OTD.
It is in the cases of illness and divorce that someone needs to reach out and make sure kids don’t find the wrong answers to “Ribboinoi shel Oilam, why.”
The bad seed – sorry, but only the Shygetz Aross approach works to determine who just has a ruach shtus or bad influences overwhelming them and who just is so far gone that they’re best off mechutz lamachane where they can’t influence others or destroy what others build.