I felt the same. But I think the reason is similar to how your fuel economy is absolutely destroyed by sitting still. When you average in a speed of zero the calculation goes haywire.

People in the US are so close to financial disaster that in order to avert disaster the US had to heavily subsidize those out of work. Many people got healthcare and unemployment benefits that would not have been otherwise available. This meant money for zero hours of work. When you average in $1/0 hours it does crazy things to the graph.

The reality is: During Covid the US rapidly adopted similar safety nets to EU countries and, in effect, aligned with their levels of poverty. Once the emergency measures ended we snapped back to our previous, precarious, poverty level.

Just my theory.