The Finnish (or Nordic) system operates on the principle on rehabilitating inmates by reintegrating them into society, they do not confine them to a “typical” prison cell like those common in America (instead it’s akin to a college dorm with amenities). There are videos talking about the Nordic prison system you can look up to get the picture.
It’s the same with Norway: as they know that “keeping inmates in a cage beating and abusing them” doesn’t help, instead rehabilities them. (Look up Halden Prison) I mean, why is it that Finland manages to maintain a low recidivism rate while it barely scratches that in the United States?
You’ve already answered your own question.
But don’t forget culture. The USA was founded by the religious extremists we (the UK) booted out hundreds of years ago.
There is a very deep, biblical/puritanical streak running through the psyche of Americans (and to a lesser extent the English speaking world) that demands extreme punishment for wrongdoing. Rehabilitation is a dirty word, it doesn’t matter if someone commits a crime again, the whole point is that if they do they rot in prison.