During times of economic stress or "when the economy is terrible", extermist groups are more likely to be created or gain power. why is that? what are some examples?

Because when the economy is terrible, the extermist groups will use the economy as an example of why they should rule... one example is the great depression

the second significant cause of the great migration was the desire of black southerners to escape segregation, known euphemistically as jim crow. rural african american southerners believed that segregation - and racism and prejudice against blacks - was significantly less intense in the north.