China has been cutting US Treaury holdings for several months. This seems to be a global trend:

“Declining foreign demand for Treasuries has come into focus given the increasing issuance of debt from the US government, raising concern the reduced number of overseas buyers could put upward pressure on US interest rates.”

https://www.ft.com/content/7b1f42fe-0246-11e9-9d01-cd4d49afbbe3

Economists differ for the reasons, but they may have some concern about the sustainability of US debt, which under Trump apparently has increased by $1.5 trillion.

Given the current trajectory, interest payment on debt will be larger than the budget for education and would, if not corrected, sooner or later surpass the Pentagon budget.