Why did Saisheng Pharmaceutical delist from the United States?

Going back to Hong Kong to increase market value. According to relevant information, Saisheng Pharmaceutical delisted from the US stock market in 20 17, and the market value of privatization in that year was $607 million. After the US stocks were delisted, the valuation of Hong Kong stocks directly increased several times. . The last company that played like this was simcere.