Single elimination tournaments are, with rare exceptions, won by the team with the best quality coaching/roster. Josh is great to be sure, but top to bottom from GM through HC all the way down to practice squad, the Chiefs have simply been better than the Bills, not by much, but enough. Everyone can see it. Reid/Spags are the best coaching duo in my lifetime-- the Bills have 1st time OC and DCs; Mahomes / Josh is probably a draw, but we have no one like Kelce or Jones, not even close.
Bills can take a meaningless regular season game when injuries at that moment, etc. / home field can make a difference and neither team is opening its entire playbook (esp. the Chiefs), but when its win or go home, having one of a kind talent almost always wins.. Bills do not have one a kind talent anywhere. Just a very good roster and organization top to bottom.
Be happy people. We are witnessing the best of the Bills 60+ year history.