Well, I don't know what's in their heads, mate, which is why I propose engagement. They might view the EU as an economic disaster for the UK, and have felt getting us out of it was the main priority, and the benefits to the economy would benefit everyone and the public purse. Maybe they considered some Labour policy disastrous. There are a milion and one things that they might be thinking.
Maybe some of them aren't thinking at all, and exhibiting the sort of tribalism I'm arguing against on here, and they have such closed minds as to believe that a rubbish one of ours is better than a genius saint on the enemy side. All I can say with certainty is that 99% of them won't be voting because they specifically want to see more homeless people, kids going hungry, and people dying because the NHS is run down. Given that, I believe there to be scope reasoned argument, even if it has to be tried repeatedly in many different ways. Giving up, and hurling abuse, achieves nothing is all I'm saying.