a) Immediate cause are also alcohol, drugs, and addiction in turn have other causes.
b) Lack of feelings, and impossibility or not willing to imagine the pain that the
crime produces to the victims (conscience and neurology).
c) the insane thought that a crime is a shortcut and that in the long run
committing crimes will bring wealth; this only happens when the crime is
perpetrated on a gigantic scale, like dictatorship, but also in these pretty
nasty cases, often their final fate is not a violent and shameful death.
d) passion, anger, something that gets out of our control.