Have you actually watched the play? It was obviously incidental, he wasn’t TRYING to step on the other player’s ankle or leg.
The still photo makes it look worse than the video but rules are rules and the officials ruled it deserved a red card. If the situation was reversed, Falungong would’ve rolled around on the ground like his foot had been decapitated and the other player would’ve been red carded. Soccer players are coached to be drama queens for this reason.