Its the only punch thrown in at least two generations, maybe three. That's a large part of the shock. When the bullied strike back against the bully, the bully is utterly staggered not at the force of the blow but that they dared to fight for themselves at all.

The crying I've seen was appropriate for a successful conclusion of operation sealion, not independence from an unelected foreign dictatorship and some international mega corporations.

The breakup of the Austrian and Ottoman empires in the early 1900s gets a lot of ink spilled. Or look at the dissolution of the concept of Iraq as a nation, currently.

Most people forget the Soviet Union broke up in the 90s without a world war. Or the British Empire dissolved with relatively low levels of bloodshed (not zero, but not "that much" compared to WWI and its continuation as WWII).

Also in binary world there are only extreme conditions and UK not being in the EU somehow magically requires a border wall and shoot to kill armed guards and extensive use of landmines and retarget all the UK nuclear arms to point at Brussels. Back to reality, the relationship will likely be as confrontational as USA-EU or maybe Switzerland-EU. Worst case maybe Turkey-EU. Or instead of comparing to EU, could compare to UK, and it'll be like Canadian-UK relations. As much as the pouters insist on being very loud incredibly sore anti-democratic losers, I'm not thinking anyone is going to send infantry brigades over anyone's border anytime soon in either direction.