Why is Hainan's population so small that Taiwan Province Province is similar to it? Why is the population tripled?

Because Taiwan Province Province is an immigrant island, in the past 500 years, in addition to native aborigines, there have been a large number of Taiwanese immigrants (including1200 million religious officials who came to with Chiang Kai-shek in 949), as well as Dutch, Spanish and Japanese left over from the colonial period. In recent decades, many Filipinos, Indonesians, Thais and Vietnamese have come to Taiwan Province Province to get married or work.