Why did Adam Smith criticize monopolizing merchants and manufacturers?

Adam Smith criticized monopolizing merchants and manufacturers because their "monopolizing spirit" and pursuit of special privileges directly inhibited the competitive system necessary for national prosperity.1

Smith argued that a system of "natural liberty" best serves the interests of society by allowing competition to regulate prices and ensure the efficient distribution of resources. However, he believed this system could not function if governments catered to the demands of merchants and manufacturers who sought to restrict trade through the "mercantile system". Smith viewed these restrictive measures—which favored monopolies at home and abroad—as obstacles to the division of labour and the steady growth of national wealth.21

Ultimately, Smith held the "mean rapacity" of these groups in contempt, asserting that they neither were, nor ought to be, the rulers of mankind. He believed that allowing such interests to influence government policy would prevent the "invisible hand" from exerting its benign, socially beneficial effects.12