Quote from mschey:
The swiss have done well because they have managed to avoid destruction from internal strife, or external forces. Their location makes them virtually unassailable by ground forces.
add some political stability on top of that and a kind of unexplainable low interest rate.
If I had to bet on one event that probably made modern Switzerland, it's the openness to welcome protestants who were hunted in other european countries. They were traditional hard working good merchants/industrials.