The overall problem that led farmers to support populism was the fact that farmers were often badly in debt. This led them to support populism for a number of reasons.
First, the farmers were led to support populism because they felt that the railroads were using their monopoly powers to exploit the farmers. The farmers needed the railroads to move their crops and each area typically only had one railroad the farmers could use. The farmers, therefore, wanted the railroads’ prices to be regulated so that they could not charge what the farmers saw as exorbitant prices.
Second, the farmers were led to support populism because they felt that the government (and the Senate in particular) had been captured by the rich. They felt that the rich (bankers in particular) dominated the Senate and prevented the government from passing laws to help farmers. They wanted the direct election of Senators to end this problem. This was an economic problem because the government, by favoring bankers, hurt farmers who were always in debt.
Finally, the farmers were led to support populism because of issues having to do with money. Because the farmers were in debt, they wanted some inflation to occur. In order for that to occur, they needed the US to go off of the gold standard. The populists supported “free silver,” which would have reduced the value of money (inflation) and made it easier for farmers to pay off their debts.