You didn't cook it long enough! H & F need to go to like 215-225 that is where most of mine are at when they come off. Then at least a min 2 hr rest. I don't use a thermo during the Cook I use the "Cowpoke Therma pen"
but I do monitor the temp once it is off the pit I let mine rest until they have coasted down to 150 that takes about 2 hrs.
The Cow Poke Therma pen