https://en.wikipedia.org/wiki/Switzerland_in_the_Napoleonic_...
IMO the main reason is that Switzerland has no natural resources so for this reason it was not invaded. You go to Africa and see the same thing, the less resources a country has, the wealthier it is.
Then you have Jews and protestant ethics in half the country that value work a lot. They welcome and support you if you are a good worker.
Then you have cold Winters that develop indoor activities like reading or workshops. They used to sleep half of the year.
But the most important thing of all, they don't have socialist or communist in power. It is a great thing that I can not vote, because the majority of workers that go there to work are leftist and will destroy the country in a few years if they could vote.
Imagine that you take the better workers, teachers, and entrepreneurs in a country and exterminate them. That is what happened in Russia and China with the communist revolutions. The most lazy and envious, aggressive and worst workers became the bosses.
That made people in those countries to literarily starve to death from incompetence and population to go down(Russia population was bigger than US of A at the start of the century). But most important, it was an inverse natural selection. The brightest and resourceful people disappeared from the genetic pool. And the culture destroyed excellence and hard work as a merit.
In Switzerland, merit culture not only survives but prospers, because without natural resources, they don't have alternatives.