I think KC is better than you say because of the coaching, but it is the case that their pythagorean record last year was 10.1-5.9, and they were helped with ridiculously close and arguably lucky wins against Atlanta, SD, Carolina, and Denver. Almost all were basically decided on the last play and involved flukes. They also went 2-0 in OT. The Atlanta game was the most ridiculous one; ATL had just gone up by one point late in the game and went for two to take a 3-point lead, and Berry returned an INT for a pick-2.
They lost one tough one to TN on the last play, but by my count they went 4-1 in nail biters. They lost 19-17 to TB, but it was 19-10 when the Chiefs scored very late (garbage time, basically). TB dominated them statistically.
Furthermore, their 6th overall DVOA ranking was bolstered by being #2 in ST; they were 13th on offense and 14th on defense. ST performance fluctuates wildly from year to year.