I'm British by birth, I chose Berlin after Brexit because:
1. Friends here
2. Alternative countries were Luxembourg/Switzerland (more expensive); Canada (worse weather); Ireland (fear I might get blamed personally for the stupid done by British politicians, and the UK Gov was being loudly stupid about Ireland at the time); USA (weird culture, guns); Australia/New Zealand (too far from the old country to visit regularly); France (I find the language harder than German); Belgium (saw a police officer with a long barrelled gun at the train station and noped out of even visiting it during an Interrail exploration trip); or somewhere where I hadn't even started learning the language.
That left Austria, which was an option, but Germany was bigger and I didn't want to risk having to move country for work before getting a permanent right to remain in the EU, which I think I need another 6-12 months for depending on what exactly counts.
Alternative cities within Germany: many pretty options, but the tech scene is mostly here, and also the friends.