Even before that Taiwan did not belong to the rest of China.
There were some settlers from the main land, but the indigenous population always controlled most of the island and the Chinese settlers were careful not to antagonize them.
This lasted for hundreds of years, pretty much until a brief period at the end of the 19th century when the Chinese government decided to send troops to brutally subjugate the indigenous population, only to shortly after lose control of Taiwan to the Japanese.
Even before that Taiwan did not belong to the rest of China.
There were some settlers from the main land, but the indigenous population always controlled most of the island and the Chinese settlers were careful not to antagonize them.
This lasted for hundreds of years, pretty much until a brief period at the end of the 19th century when the Chinese government decided to send troops to brutally subjugate the indigenous population, only to shortly after lose control of Taiwan to the Japanese.