A lot of different reasons for it probably.
The inverted yield curve unraveling is certainly part of it.
Inflation is still a big concern on main street even if the CPI says it isn't. I need higher yields to lock my money up long term if I feel the rate isn't that far off from the inflation rate.
Maybe our debt isn't that attractive right now. Changing administration means a different fiscal policy. Maybe people are taking a wait see approach.
I also think the Fed doesn't have nearly as much influence on long term rates as short term.