Every study ever done has shown that kids are significantly safer in the back seat. All kids should remain in the back seat until they are old enough to drive, according to crash statistics.
Sweden is not North America. They have different vehicles, primarily a much newer fleet of vehicles. Their vehicles have different safety standards than ours do.
Yes, there is a crumple zone in front. But it isn't always enough. When there is intrusion, it is most likely to happen in the front. The farther you are from the point of impact, the better off you are. Front vs back doesn't matter for side impacts, so really we're only looking at frontal vs rear impacts. Frontal impacts are both much more common and much more severe than rear impacts.
I've driven with my DD in the "front" seat of a moving truck (no back seat, obviously). There was no airbag to worry about. She was riding in a Radian, one of the lowest profile seats available. She still significantly interfered with my view out the side window and to the side view mirror on that side, and I moved her out of that truck ASAP. So that's another consideration when you're talking about a child in a car seat in front, especially a rear facing seat. The seat likely blocks the driver's view, or interferes with the driver's ability to comfortably reach the controls, or both.