Most criminals are really, really stupid.
John Douglas, the FBI Profiler, would say that it goes along with the childish attitude “I can take anything I want”. Then the greed, and maybe not being caught or confronted, keeps the snowball rolling to bigger and bigger grabs as the thrill to the lesser grabs is gone.
He says most criminals are not the masterminds shown on TV. Most do not have intricate thinking, but develop something that seems to work and then keep following and developing from that.