I suspect that the people who vote nationalistic populists into power are less interested in European elections.
And possibly these voters also dislike the amount of water the PVV has already had to add to their wine to get a coalition going on national level. Water such as guarantees that the constitution is not blatently broken.
It is a matter of responsibility. If you can log into any lemmy instance or mastodon server with the same account, then which server takes responsibility for your actions in the fediverse?
I have seen instances be defederate from because of their lax account creation requirements, or because of harrasment from users from a specific instance.
If an account can log into any instance, then who is responsible for banning the account?