The original post to which I responded stated "Defender throws up hands and deflects ball into the goal. (clear and obvious handling.)"
Of course, on the field, it is not always so clear and obvious that it was deliberate handling of the ball. IFAB now includes with the laws of the game factors for the referee to consider
- the movement of the hand towards the ball (not the ball towards the hand)
- the distance between the opponent and the ball (unexpected ball)
- the position of the hand does not necessarily mean that there is an infringement
- touching the ball with an object held in the hand (clothing, shinguard, etc.) is an infringement
- hitting the ball with a thrown object (boot, shinguard, etc.) is an infringement
IMO, these address the question: why would a defender do that? When there is a good reason, the action is usually deliberate.