I don't think Reid's issues have anything to do with it.
The o-line is bad this year, the running game is affected by this, they are really thin at wr, and the defense is horrible.
Heck Josh would struggle playing on this Chiefs team.
Mahomes would take this Bills team to the SB.
If you think Mahomes is done, just look at the first four games of this season. He was on fire. This team has been affected by the usual things a dynasty/ mini dynasty goes through. Can't afford to keep everyone, players are aging and injuries. In the NFL, winning catches up to you by design.