Europe is not a monolith and I don't know why people think it is. 2 years stints are not unusual at all in London.

London is economically, politically, geographically, and culturally fairly distinct from continental Europe.

It's about equity worth nothing jn Europe as an employee. Europe is a bad place for employees to join a startup. Lots of time people are attracted with shares/stars whatever. Only to find out they get nothing or are taxed to hell. There is a reason why Europe is failing.