I agree with the second part, not so much the first. If the Treasury had financed $10T with long term bonds the primary buyers would have been banks and other institutional investors, and when rates jumped suddenly in ‘22 the banking sector would have become insolvent overnight, with insurers soon the follow,
The Treasury does make sure there is liquidity across all maturities, so they have to follow demand, which is very strong at the short end, and with 10 year bonds, which are the preferred choice of hedge funds.
The bond market is self-correcting. If there is inadequate demand to finance the debt at lower rates, those rates will rise. That’s when it gets painful.