Why on earth is my heir, who owns some land, plotting to claim parts of my territory and individual duchies? Doesn't make sense since he is going to inherit the whole damn kingdom (all three of them) soon anyway.
Because AI doesn't have normal human sense and emotions, it does stupid things from a human perspective. Or it can think like a psychopath: whatever it rationally believes to be good to it (however misguided in reality) without being swayed by emotion or empathy. Basically comes down to defining some variables to determine AI behaviour. After a while of playing, for example, I'm sick of all the plotted murders around me, including people with good character traits trying to assassinate infants.