Brexit occurred because of an (absolutely imbecilic) political gamble that failed quite catastrophically and the opposition party (that subsequently gained power) latched onto the idea and wouldn’t let go.
Edit: it was the Torries, soup to nuts. Not sure how I crossed that one up lol
This is occurring because all the countries in question underwent military coups recently (with possible-to-likely Russian - specifically, Wagner - backing). The military juntas that are now in charge are doing this. This is categorically not a democratically-motivated change.