Defense wins championships

The Eagles offense, as good as they were, did benefit from a few short fields thanks to the D.
The flip side of that is the offense being able to move the ball and score off of those opportunities put pressure on the Chiefs offense which helped the defense. The Eagles offense, defense and special teams in combination one that game.

Look at all the field goals the kicker made. If he misses any of those it's points not scored and gives the Chiefs better starting field position.