Its a regular phenomenon for one or the other reason from time to time..
These days every government treat the stock market as their indication of 'performance'.. so you won't be surprised by the effort (monetary? policy?) put in to show they are doing a good job. Look at Japan if you want a good example.. Wonder when will they let go of their holding of Tokyo market.. in 98 during the Asia crisis HK Govt went in to buy a chunk of stocks to hold the index, and they subsequently put those all out using the 2800 ETF. Now J MOF already hold their stocks in ETFs.. are they going to let those go ?
Might be worth a quick read... these guys seem to know their china tech.
https://www.protocol.com/newsletters...stocks-carnage