They are in a position of having no seas and only EU on every side, which means things are getting more bureaucratic the more EU-Swiss relationship sours. Think border checks on the ground and flight restrictions in the air and the less than 10M rich people in the mountains can now trade only among themselves.
Why would the EU be so irrationally butt hurt about it? It seems easy enough to let the Swiss have their policy and both continue to benefit
Edit: EU can void all the other contracts, but why would it want to? Why do they care so much about how many immigrants Switzerland has?