Carlos Slim Helú inherited a significant amount of money from his father, then Slim made his own investments that greatly increased his wealth. During Mexico's 1982 economic crash, Slim invested in the collapsing businesses, picking up managing shares in many companies and later making a profit as the economy rebounded. According to a 2014 Forbes biography, Slim has a net worth of just more than $72 billion.
In 1980, Slim had already established himself as a businessman and had a portfolio with more than a dozen companies. During the economic crash, Slim was able to purchase large shares in several more companies, including the Mexican division of The Hershey Corporation, General Tire and British American Tobacco.
Slim's biggest business move was buying Telmex, the preeminent Mexican phone company of the '80s and '90s. He developed Telcel, a mobile phone company, to work in tandem with Telmex. These phone companies control 90 percent of Mexican landlines and 80 percent of cellphone coverage in the country. Slim's virtual monopoly over Mexico's telecom industry allowed him to develop communications-related business interests internationally. Though Slim once managed Telmex and Telcel with France Telecom and Southwestern Bell, many of the companies' daily operations are now managed by Slim's sons.
Carlos Slim is rich because he monopolized the phone companies in Mexico. All the home phone & Cell phone services are part of his company. Also, he has business with drug cartels
Carlos Slim Helu has dominated Mexico's telephone industry since he bought the state-run telephone company Telmex in 1990 and spun it off into America Movil. report this answer. Updated