First off, there is the issue of currency / gold standard / bimetallic (silver was introduced along side gold). William Jennings Bryant was popping up on the scene as an ardent opponent of not only gold but also large corporations and railroads.
Secondly, it was the first time that people weren't more or less self employed (mostly has farmers). With industry popping up, there were large numbers of people employed in factories and other industrial settings that required large numbers of workers.