That's part of it another is that the right offers some easy answers to some very complex questions. They aren't the right answers but they're easier to wrap your head around. As prosperity drops, the time, effort and resources the average person can commit to understanding the complex problems facing their country also drop. This means the easy answers take root easier, and spread further and faster because the less informed are less resilient to them.

I think for many people who feel desperate, everything starts to look like a zero-sum game.

This is a good observation

It often happens when a society's prosperity decays

It will be interesting to see whether the far right rises in a country like Denmark, which afaik still has the definition of a well functioning social safety net.