Of course it helps if the city, and country in general, is completely flat. Cities in Norway or Nepal have mother nature against all form of manual locomotion.
I think Norway is more about being comfortable riding in the cold on spiked tires. The hills of Oslo don’t bother you after a couple months of riding them.
In Trondheim, Norway we have the famous bycicle lift. :)
Are you a time traveler from 2010 who's never heard of e-bikes?
Actually, I don't think it's a huge coincidence that a lot of cities are relatively flat, because they tended to develop near larger bodies of water.
Oslo is #18 on that list, not too shabby. Kathmandu is in a valley.