Why is Hainan's space launch site under construction often not optimistic?

As early as the 1960s and 1970s, when the country chose the launch site, Hainan was considered by experts several times. At that time, although Hainan was economically backward, most of the mountains and beaches were still desolate, but this was not the main reason for giving up the choice. Because, in the extraordinary period of national defense engineering, in order to keep secret and reduce immigration, we must choose such a place. Hainan was not favored several times, mainly because the surrounding environment of China was very bad at that time, and everything was based on preparation. Hainan's combat readiness is obviously not conducive to the construction of costly national defense projects. Until the location of manned space flight, Hainan was once again included in the alternative plan, but it was eventually rejected on the grounds of confidentiality and investment.