Why has Hong Kong become a "refugee paradise"?

I recently read the book Slums in the World Center: chungking mansions. I mentioned in my book that many households in chungking mansions are refugees awaiting approval from the United Nations and the Hong Kong Immigration Department. I have also mentioned many times that there are many refugees from Africa and South Asia in Hong Kong. Due to the limitation of discussion topics, the book does not explain why refugees came to Hong Kong. In the recent "Snowden incident", Snowden's preferred destination after leaving the United States was also Hong Kong. Without geographical proximity, Africans and Americans went to Hong Kong to take refuge. Later, we found that Hong Kong had a history of receiving a large number of Vietnamese refugees in the 1980s. Some mainlanders who are temporarily unable to return to China for political reasons also choose to stay in Hong Kong, such as the North Island. Some local people in Hong Kong say that Hong Kong is regarded as a "refugee paradise" by the outside world.