Why do people vote against their own interests?

I totally forgot what it was that I had planned to write about populism, but in any case, the BBC has a very depressing article saying it much better than I ever could. This part makes me feel ill:

It's like a French Revolution in reverse in which the workers come pouring down the street screaming more power to the aristocracy.

If that doesn't say it all, then the nauseating picture accompanying that article certainly does.