The Norwegian system, unlike others, is fully committed to rehabilitation of criminals: you are not punished but helped to go back to an honest life.
In this view relatively short sentences and comfortable prisons are part of the rehabilitation process.
How many really bad criminals are capable of rehabilitation, though? And I am not talking only of psychotic terrorists like Breivik, I am talking of brutal criminals who make killing people a way of life. Mob enforces, bosses, drug lords and their underlings, human traffickers, etc. Rehabilitation is a fine concept but many are simply beyond redemption.