Fair point, it’s a small world after all (even more so in Switzerland).
There’s also another side to this:
I’ve seen accomplished professionals leave (not pushed out) and do so in a completely professional manner after having done a very good job for a prolonged period of time at company X, yet get trash talked afterwards nonetheless. Companies after all are filled with people and in a corporate environment the most nasty parts of human nature can have a good place to rise up.
I’ve also noticed (working for multiple companies) that in the end most people won’t go out of their way to do something inherently bad (e.g. steal money) but the vast majority of people will look the other way and not speak up when they see somebody else doing something bad.
When I hear people talking negatively about somebody else (especially somebody who’s no longer there) I always take it with a (big) grain of salt and question their motive.