Why couldn't stocks make this move when UST was at the bottom of the bell curve?

You will notice this move in stocks is vastly under-performing UST today.   My interpretation of this move is because UST was above the day's center of value when stocks made their move.  For this reason, the large treasury traders could not buy bonds cheap, so, they haven't gotten involved yet.

However, this move in stocks gives me even more conviction to buy a dip in UST over the next week if we get one.