Materially, it makes little sense for blue-collar workers to vote for Modi, Orban, or Trump, a billionaire whose platform is to cut taxes for the rich. Hitler and Mussolini had their share of support from the poor too.

What are some of the theories of why this happens?

I know scapegoating foreigners for poverty is part of it. Wilhelm Reich wrote The Mass Psychology of Fascism but I haven't read it.