Why would FTX want to carry out such operations and actions? One view is that this may be for self-interest, as a way to maintain liquidity and offset losses in other investments.
According to YouTuber DivXMaN (@crypto_div), FTX may have run into liquidity issues by gambling customer funds, so keeping the price of Bitcoin low would ensure they are better able to handle withdrawal requests during times of liquidity stress. In addition to this, low Bitcoin prices also depress the prices of other assets, providing higher upside as they attempt to trade their way out of the problem.