There's this theory that was suggested by a French geographer in 1989.
The Blue Banana
Lol, I find the name of it to be cool.
It just states that the most dense areas of the continent have been the most creative and wealthiest for 1000 years or so, which makes sense simply because human resources and exchanges over these areas are more intense than in countrysides with a low population density, where life tends to be rougher.
Hence the difference between West and East Germany that would go back further into the past than the Soviet occupation, for instance.
I suppose it's an interesting theory, though it wouldn't be enough to explain the extraordinary wealth and standard of living of Switzerland.
Besides, some areas like Scandinavia are not included in the banana, while they manage to maintain a fairly high standard of living too, so density wouldn't explain everything.
It's nonetheless definitely an important factor.