I think most people that voted for it didn't care about it. It was about "taking back our borders" and "regaining out sovereignty" and all sorts of other bullshit. They wanted away from big bureaucracy, wanted to relive the British dream of being a powerful independent nation that just gets what it wants, when it wants it, and who cares about all that free trade nonsense, I'm just selling to the folks in my community, not them bloody Europeans.
That doesn't apply to everyone, but quite a lot. And once you commit to the idea of such a major change based on ideological reasons, you don't need to look too deeply into the facts, you just like hearing the people on your side say good things about the decision you've made.
At the end of the day the UK and the EU were intertwined in so many different ways that unless you were fully invested in the details, you wouldn't be able to fathom all of the negative impacts, and "the nation is tired of experts", so just leave that to the politicians. And when things don't work out, just stick with the EU as the bogeyman. The only thing that might start to become clear at this point is how much weaker the UK is in comparison to the EU now. It's hard to avoid that recognition.
Then there's the rich Brexiteers who made money in the financial markets, so they'll take the long term hit as they've ran away with their bags of money.
The whole thing is a shambles over and over again.