For what reason did John Stuart Mill believe the government should get involved in the economy

Although derived from the tradition of unlimited laissez-faire, Mill repeatedly takes the position of some kind of interventionism. Generally in favor of the economy in which the state as "Night watchman", should be designed only to create a suitable climate for the free economic initiative recognizes that this solution can lead to dangerous monopolies, and thus the denial of the right to free activity of every citizen. In other words, J. S. Mill notes that the application of the principle of laissez-faire in the strict sense of the word leads or may lead to undermine free competition. Some critics of Mill remarked that these measures are ineffective and that state interventionism create monopoly itself