I don't get it. If they knew this was going to hurt their economy, why would they vote for this? I guess I don't really understand why they're voting to leave the EU to begin with.
BREXIT side used a lot of appeal to fears and scared people with the immigrants and refugees. They also relied on peoples hate of bureaucracy and they claimed that UK is giving more money to the EU than they gain from it. Which relies on faulty logic as many of the benefits from being a member of EU are hard to count. Like the free mobility in Europe that was bringing in foreign talent to UK and helping UK citizens find work abroad (which reminds me, an old roommate of mine is living in UK and I wonder if he has to take his family and leave now...) not to mention that the foreign trade is going to get a lot more complicated and rather than trading with a bunch of separate countries that make up Europe UK will now have to make trade deals with a united EU so they can't find a weak link that they could influence individually. Though the rest of the world is still the same any dealings with EU are going to cost a lot more.
...Partially because this was also a big blow to EU and if they let UK get off easy this will make other countries think that they can get out of EU and still reap the benefits.
EDIT: This was also a good example of why being right is not the most important thing if you are trying to influence people. BREXIT side was better at making people believe them and encourage them to vote. Simply relying on "the British people can't be that stupid" has come to bite the British in the ass. The other side really was too quiet as they were certain of their victory, they didn't work for the victory and although celebrities like Eddie Izzard tried to campaign for staying in UK it was too little, too late.