Why is flopping so effective? Maybe it's because empathy is a reflexive feeling in many people. We care when we see other people fall over, if only for a moment, before we've taken stock of the situation and realized that we've been played for dupes.
The free kick above may not have worked if the man taking had simply tapped the ball to his right with his foot. No, he needed that moment's hesitation, he need to fall over and ignite the human capacity for concern and subsequent confusion in his opponents.
In that way, he did much more than simply assist a goal. He made sure that his opponents would never be able to trust their feelings again, and that every moment of compassion they show to another from now until their dying breath will be foggy with distrust.
What a doofus.