|EU organisation diagram|
I can’t speak for my country.
I personally think the proximate cause was the unwillingness of the EU during Cameron’s negotiations to offer even minimal gestures towards reforming those policy areas that raised concern in the UK. They did this in the full knowledge that Cameron needed a deal he could sell to the electorate. Instead, he was humiliated. After a widely-derided effort to suggest that he’d obtained worthwhile concessions, he effectively had to drop the whole subject of the supposed reforms from the referendum campaign.
In respect of immigration, the critical issue was the way the economically-unsound idea of free movement of people had quietly replaced the economically-sound idea of free movement of workers in EU treaties. The latter is about allowing factors of production to move to areas of gainful employment; the former only makes sense as part of a political project and throws intolerable burdens on to the public and social services of richer member countries. It’s worth noting that other members subsequently adopted restrictions they’d refused to Cameron.
Let us also for a moment consider the alternative to the UK leaving. Remainers argue their position was the status quo; it was not. The EU has two major projects that define its objectives; these are the Schengen Agreement on open borders and the Euro single currency. The UK had already decided to opt out of both. We had no influence on these two central issues. Hence we could only ever have been a fringe member going forward.
In particular the Eurozone members collectively outvote the non-members in the EU. They meet together, without the non-members, in order to agree a common position before EU Council meetings. One Eurozone meeting even decided to commit EU funds to a bailout scheme despite the UK, a major contributor to EU funds, not being present at the table.
In summary, I rather think the EU left the UK.