China used to buy US debt to prop-up the US dollar so that the USA could purchase Chinese-made goods. Then, as Trump and Biden began to put sanctions and import limits and stuff on China, they CCP began to look for alternative markets and even began to attempt to grow their domestic market. Now, having lowered their exposure to US trade retaliation, China is also lowering its exposure to US financial shenanigans. It has been dumping US securities increasingly over the past couple of years.