Yes, radicalism increases during periods of economic or cultural convulsion, because people are looking for solutions to complicated problems. With economic problems, like in the Weimar Republic, people start to look for other people to blame for their problems. They look for scapegoats and other reasons for the problems, and that leads to radicalism.
Anytime people face adversity, you find out their true colors. Many people are just looking for an excuse to be bad because that is who they are. In times of economic crisis they get to say, "see we told you so." Then they make up a bunch of propaganda to get the less knowledgeable people scared. It makes them panic and they join the rank and file of the radicals.
I definitely think that there are more radicalism during times where the economy and culture is facing difficult times. I think that it is only natural that there are a lot of emotions during such periods of times in a nation. When countries are facing such things, it is important to be careful of such behavior.
Any time a nation goes through great economic or cultural change there are going to be those who go to the extremes and become radicals, some don't wish for changes to occur and will radically try to bring back the period before the old changes and some will become radicals trying to push the changes even further.
Radicalism definitely increases during times of economical and or cultural upheaval. It is the nature of mankind to form alliances among one another to take a stand or even make demands for change in socially relevant instances. There is no chance that in a society, 100% of the population will ever agree.