Roughly 40-60 million years ago, the area significantly rose and fell as a result of the folding of the Alps, and the area was flooded by a sea. This event happened several times, as recent as perhaps 5 million years ago, and many fossils of snails, shells and even shark teeth can be found today in such a high altitude. The events made the area relatively flat for a mountainous area, making it more habitable for living and growing crops.
If you’re interested in visiting the Swiss Plateau, I’d recommend staying in the Backpackers Villa Sonnenhof, which is a great hostel located in Interlaken, Switzerland. I'd recommend staying in hostels while traveling Switzerland, and they are a quality one that gives you the greatest value.