The Chiefs are like that Simpson episode where Homer was a boxer. Essentially he had a condition where he was able to take such a beating in the ring he would let his opponents tire himself out while he just stood there and did nothing and he would just push them over after they were exhausted from punching themselves out. That's sort of what the Chiefs do: they play conservatively, don't turn the ball over, play good defense and rely on the other team to make mistakes and they win.
The problem is that you eventually have to play well to win(to finish the analogy, Homer ended up fighting Drederick Tatum - a pastiche of Mike Tyson - who wasn't going to tire out). The Chiefs fail because they're going to have to go up against really good teams in the playoffs and they'll have to play well because those teams aren't going to beat themselves 9 times out of 10.