They won the Super Bowl! That's a big jump from 7-9. It wasn't a simple improvement.
Watching the Packers and Saints games and even the Super Bowl, you could see Brady had a huge role in it and he made killer throws that cut the hearts of the opponent. People talk about the 2nd half defensive demolition of the Chiefs but the fact is, the offense piled on points in the first half and then they just went into cruise control and sat on the lead as the D demolished them.
The offense put up 21 points in the first half. After the first series, look at what the offense did in the next 5 possessions: 34 plays, 327 yards, 28 points.
That was in 26 minutes of play. The offense put on a fireworks display for those 26 minutes, and that's all they needed to do. They put KC in a hole. Anyone who credits the D for that blowout only is deluding themselves. Reminds me of what they say about the Patriots Carolina Super Bowl when the offense similarly went off.