"The EU did not "let the UK leave", it did everything it could to prevent that outcome "
You mean they wouldn't let the UK out without a border or paying the money they owe? So, they were being sensible then? Also, Greece would have been a lot worse off if the EU hadn't stepped in as they haven't controlled their own inflation in decades. They also have HUGE amounts of corruption throughout their country and waste money everywhere. You can't blame the EU for trying to reel them in.
Similar in Spain. If they are going to pin all their hopes on Tourism while selling all the good houses to foreigners, where do they expect to get money from? Don't blame the EU for nations making bad decisions. Same as trying to blame the EU for France not following the EU's advice, leading to the gilets jaunes movement.
Trying to blame the EU for nationalist idiots burning their own countries is beyond stupid.