The shock over the bond market isn’t how high it is exactly but how traditionally the bond market is an inversion of the equities markets. So you’d usually see bonds down while equities are up. And then in an equities dip or downturn bonds are a nice hedge/flight to safety so the buy rate goes up.
What you don’t usually see is bonds down and markets down driving yields up - so to have both at the same time means that bonds (US treasuries) are not a safe bet.
Apologies if this is posted everywhere - there just seemed to be questions on the forum asking about why the yield being up was a bad thing because it’s so recently been up