We celebrate the victory of our Champions, though we haven't expended a calorie of effort ourselves. They represent us - clothing themselves in our colours (and we in theirs). Because of our connection, their victory is our victory.
Just so, Jesus takes on our condition, clothes Himself in our humanity. And His victory is our victory.
Knowing Christ as Champion is the chief article and foundation of the gospel...
Martin Luther: “The chief article and foundation of the gospel is that before you take Christ as an example, you accept and recognize him as a gift, as a present that God has given you and that is your own. This means that when you see or hear of Christ doing or suffering something, you do not doubt that Christ himself, with his deeds and suffering, belongs to you. On this you may depend as surely as if you had done it yourself; indeed as if you were Christ himself. See, this is what it means to have a proper grasp of the gospel.”