I found an article about overseas Chinese business and offshore Chinese business network when searching some stuff for my exam. It might be less important now, but Shantou indeed was one of the first five Special Economic Zones (SEZs) that set up by Deng Xiaoping for economic reform experiment. And the main reason is described in that article as:
In 1980, when Deng Xiaoping began the process of opening China by setting up Special Economic Zones, free market enclaves on the southern border, he chose the ancestral homes of three of the most important groups of the Chinese diaspora: the Cantonese from Guangdong province, who predominate in Hong Kong; the Hokkienese from Fujian province, who make up 85 per cent of Taiwan’s population and much of Singapore’s; and, less well known, the Teochews from around Shantou, on the border between Guangdong and Fujian.
The Teochews are a phenomenon. They include Li Ka-shing, Hong Kong’s most respected billionaire; the Ma family, which controls the Oriental Press Group there (and which fell out with the British Conservative party, accusing it of failing to deliver on promises made in return for campaign funding); and most of the Chinese in Thailand, including the Sophonpanich family who built up the Bangkok Bank. (The Lamsams of Thailand are Hakkas, a group of unknown geographic origin, which has produced the three most influential Chinese of the late 20th century-Deng Xiaoping, Lee Kuan Yew and Lee Teng-hui, the president of Taiwan).
For those who are about to travel to Shantou and want to know about the city, this might be something worth to explore into.