Because the country has humiliated itself on the world stage, proved to be run by a scabby band of self interested morons and half populated by backwards facing

Because the country has humiliated itself on the world stage, proved to be run by a scabby band of self interested morons and half populated by backwards facing gullable isolationists, willing to burn 50 years of hard won progress and risk destablishing Europe, just at the point where we face huge global environmental and economic challenges, at a time when it’s clear that working togther is of paramount importance. Just a guess :)