Why not Hainan instead of Taiwan?

Nov 2017
Geneva, Switzerland
The Portuguese, Dutch and Europeans in general showed interest in all of Asia, the Americans tried to buy Taiwan, the Japanese annexed Taiwan after the Sino-Japanese war, the French who were right on the hainan side in Indochina did not colonize it, the British even with the opium wars.
I ask what hainan has prevented his conquest in comparison to Taiwan and the rest of Asia?