You stated that you did not fill through the upper radiator hose.

You then asked if we had any ideas. Clearly, you had doubts about your procedure.

You asked a question and answered it yourself. Your problem is the failure to properly fill the head with coolant. The thermostat blocks the capability to fill the head until the thermostat opens. Then, all the trapped air must slowly escape via the expansion tank. It's a very inefficient way to bleed the system.

If you fill the upper hose, the coolant goes right to the head and the air in the head is immediately displaced. The engine will then run at the proper temperature immediately.