Democratic vote which has since then been proved to be heavily influenced by the Cambridge Analytica campaign, so which probably did not reflect the actual opinion of the population. It was a manipulated vote.
I remember the UK government at the time spent £9.3 million of taxpayer's money to push a pro-EU leaflet out [1], not to mention a concerted effort from the news media. It's not as if there was not strong campaigning happening on both sides.
