It was a soft penalty, but it was a penalty. Defender impeded or
pushed Mbappe off his path to the ball. He basically gave him
a hockey check (lol), and Mbappe went down. The ball was playable
as a possible header.

Also, soccer doesn’t need to have a catch-ability rule, because hands are not
used by field players. And aerial passes can be played by the player’s head.
Again, Mbappe could have made a header play on the ball.