Most of the land, is actually owned by the HK government. When the HK government wants to allocated more land for housing, converting forested land to public housing, they've historically faced lawsuits from environmentalist groups. And these lawsuits drag on for years before construction can even start.
7% of HK's land is allocated for housing, and 74% allocated for nature parks and reservoirs. With such limited supply, property prices remain high. And unlike the PAP government, HK government derives a lot of their budget from land sales and high property prices.