WHO IS ACTUALLY BUYING THE MASSIVELY SURGING US DEBT?

Since March 2020 the US National Debt has exploded higher by historically unprecedented amounts. In only 15 months it has surged by $4.7 trillion to $28.14 trillion. This takes it to 128% of GDP in present dollars.

Who is buying this massive amount of debt? Surprisingly, It isn't who everyone believes it is! Maybe even more importantly is why and how they are doing it?