It's not a matter of feeling secure or insecure.

The economic aspects of the brexit aspects were over dramatised to a ridiculous amount, and when none of the doom prophecies have come to fruition, remain voters refuse to admit it

Even the head of the remain campaign admitted it

https://www.itv.com/news/2021-06-10/it-was-project-fear-and-it-didnt-work-head-of-remain-campaign-says-economic-dangers-of-brexit-were-exaggerated

Brexit was a political decision, and they come with costs, but the UK financial services industry just added more headcount to European desks. The traders press the button in the EU, but the trades happen in London.

So when people say omg 1.2 trillion in assets moved, it doesn't really mean anything. It's just on a server in Utrecht instead of London.