Why did farmers blame railroads, banks and Eastern manufacturers?

Canadian experience was similar with a little bit of a twist. Some blamed those south of the border.
Prairie provinces: Alberta, Saskatchewan, and Manitoba developed a strong co-operative movement. For many years about the only privately owned (especially prominent) grain elevator operation was 'Pioneer'. There were United Grain Growers, a co-operative quite visible in Alberta and Manitoba and the Saskatchewan Wheat Pool in Saskatchewan. The Government of Canada set up the Canadian Wheat Board to stabilize the price of wheat for all farmers. Basically every farmer would sell to the Wheat Board and get a check for the same amount per bushel of grain (for the same grade of grain). I think this even took care of transportation from the elevator through to the port used to take it out of the country or to the door of the mill turning it into flour. Western farmers became politically engaged starting up political parties on both the right and left. Also there were many Co-op stores for groceries and dry goods (along with farm supplies) opened. If you tried to compete with them privately you would often go 'belly up' almost automatically. Then to compete with the banks were the local Credit Unions. If you are doing a paper on the topic you might like to look at Canadian sources. Some of what I have mentioned may be a little later in history than the period you are considering since Canada's west was settled a little later on.

It was discontent. The railroads, government and banks and some of the manufacturers of the time were out to make money not only to make it all the way to the west coast. They had the chance to produce, use and distribute the things that would make lots of the money they saw in the investment of the railroads.

The farmers on the other hand saw this as a way to take their land they had worked so hard to get and on to make it in the west. The railways had the right to go in and buy out not only farms but in some cases whole towns to achieve their goals building the rails. Would you feel the same if they came and took your land? You have to get behind the person this affected to see it the way they would.