You also see this in countries still in the EU and it will happen as long as we will not have true integration, it is always easier to blame the EU for your own failings, since it is harder for the EU to fend for itself in national politics.

One recent example in my country is nitrogen deposition. Long ago, countries have committed to keeping certain nature reserves in good health (or improving them when necessary). Then many subsequent governments always chose the side of the farmers at the detriment of nature. Now many reserves' soil quality is in a terrible state and the courts have told the government to stop and fix the problem. Then we got a bunch of right-wing populist countries that have wasted many more years by blaming the EU and questioning scientific methods for measuring deposits - while it has been abundantly for a long time what actually needs to be done, buy out farmers.

At any rate, this constant undermining and blaming of the EU has the effect you'd expect it to - it destroys trust in the EU. Ironically, the saving grace now seems to be the agressor and the lost ally. More people realize that we can't act in an increasingly hostile world as small and mid-sized countries.