There's a reason why Finland or Canada or Alaska are sparsely populated: The weather.
Sure, those people who can be bothered with it might pick up the cycle during the winter. Those people who can't be bothered are going to pick up their stuff and leave.
I'm from one of those northern areas. Very few people leave because of the weather even if they don't like it. It's mostly because of studying and career opportunities.
North is sparsely populated because the crops were historically poor and prone to losses due to weather conditions, not because people don't like the weather.
What sort of gear do you need for conditions like that? During one cold snap, my chain literally froze on a long ride through some light rain/sleet. (No, I don't know how that happened, but it did.)
And that was in the Seattle area, where it rarely gets all that cold.
I was a Mormon missionary in Hokkaido in some of the snowiest places in the world and got around just fine using a cheap mountain bike. The only additional "equipment" needed was a lighter, to thaw out my bike lock when it would freeze shut.
I looked up Trondheim, NO weather. It's only Rhode Island cold not Minnesota cold. Plenty of people in Providence, RI bike in the Winter. Trondheim also doesn't have the range found in either RI or MN so you don't get ridiculous heat and humidity to bike in.
Sure, those people who can be bothered with it might pick up the cycle during the winter. Those people who can't be bothered are going to pick up their stuff and leave.