Why did Zheng Chenggong immigrate to Taiwan Province Province later?

Zheng Zhilong, a pirate, was recruited in the late Ming Dynasty. Zheng fought against the Qing Dynasty in the southeast coastal area, but he was ready to retreat to Taiwan Province Province. By the way, he cleaned up the Dutch who occupied Taiwan Province Province and began to dominate Taiwan Province Province. Zheng Zhilong's son, Zheng Chenggong, had a brilliant strategy, taking Taiwan Province Province as a stronghold and constantly harassing the Qing Dynasty, which ruled this land, with powerful warships. The banner is Ming, and the title is Yanping County King, which was sealed by Nanming Xiao Wang, and it is not very valuable. Later, Zheng Chenggong's grandson surrendered to Kangxi under the banner of national reunification.