There is one way of understanding the many hard to answer questions about humans; one organizational model, the vedic-karmic model
Many ways exist to analyze and explain peoples' choices, nature-nurture, biology, neurology, psychology, affluenza, more. All reveal something of truth. The model of karma suggests desires bring actions, actions create habits, habits steer our trajectories.
Our desires and trajectories can be unwholesome. Confused 'self' is the source of self-injuring stupidity.
I suggest we, as though, see some people going up and some down the karmic ladder.
"Me" crowds out the 'we' in humanity.
Sadly downward bound souls demonstrate pashu-mentality, like dogs fighting over a dry bone.
Happily the upward bound trajectory manifests in truth and reality and morality and good-society.
Big egos make big mistakes.