Sentence:  But through the oligopoly, charcoal fuel proliferated throughout London's trades and industries. By the 1200s, brewers and bakers, tilemakers, glassblowers, pottery producers, and a range of other craftsmen all became hour-to-hour consumers of charcoal. This only <WSD>magnified</WSD> the indispensable nature of the oligopolists. 
Meaning of the word marked with <WSD> tags:  To make (something) larger or more important. (from 14th c.)