What underlying principle of capitalism causes the plant Jurgis has found work in to close?

The jobs that Jurgis holds in these two industries helps Sinclair show how tangled the web of capitalism had become in the United States. Although Sinclair does not make the connection explicitly, his readers would have surely known about the connection between the Harvester Trust, the Steel Trust, and the Beef Trust. The Harvester Trust was actually majority-owned by the leaders of the other great monopolistic industries of the time (steel, beef, sugar, and oil). Each of these enterprises cut deals with the other to get labor and materials cheaper than would otherwise be available.