There is no actual, fundamental requirement for anyone to move anything anywhere in the wake of Brexit. The reason people have described this as "inevitable" is because the EU can be assured to mandate it, even though they don't have to, even though other regions don't mind having financial services provided by the UK.
You're treating the EU's behaviour as if it's the laws of physics. That's how you know that there are fanatics in the room: people stop treating their behaviour as something that can be reasoned with, and start treating it as if they were some artifact of natural laws.
It's a false statement. The EU wants you to believe that. It is entirely false. There is no "have". There is only "want".
I'm exaggerating for effect, but the EU has a clear set of rules. It's not fanaticism, it's called "working together". The UK, not the EU, decided to stop following the rules. It makes no sense for the EU to bend the rules.
I think you've got this the wrong way round. The UK voted to leave the EU, and its not like nobody in the run up mentioned that it might lead to companies leaving the UK for EU countries. We made this bed. Time to sleep in it.