When it comes to being a financial hub English as a global language is paramount in modern world. You wouldn't expect a C-level executive from other side of the world to speak German. Further, if you've ever been in the financial scene in Frankfurt, it's unfortunately predominantly in German because most of the old people working in the institutions can only speak vacation English and they switch to German as soon possible.

Also from where did you hear that Frankfurt gets the business that's leaving London? What is your source? That was the hope for the Germans with the Brexit, but it never happened. German laws and bureaucracy is still far too hostile and outdated compared to London.

Yes but we Germans are too stuck up with our language barriers.

Euronext collectively is big, but Euronext Dublin is about 1/27th the size of LSE by its own market cap.

https://en.wikipedia.org/wiki/Euronext_Dublin

https://en.wikipedia.org/wiki/London_Stock_Exchange

That said, I'm not entirely clear how the exchange's market cap should or shouldn't be thought of in terms of the total market cap of assets that the exchange lets you trade. Or indeed the float of those assets, which is a concept I've only learned about due to SpaceX's nonsense IPO, so take my thoughts with an appropriate pinch of salt.

Ireland is a tax-haven, not a financial hub.