feddit.uk was registered last June, just like feddit.nl. Feddit.de was changed in August 2021. Unless the domains were transferred, feddit.de is the oldest
Why not? To discuss stuff in the local language and discuss local news obviously. A local instance makes sense for that. Also allows you to place the server close by the country so that you get low latency.
We have more cultures, languages, and national identities clustered in Europe than anywhere else in the world. Naturally people want an instance for their own.