To me, he's tried to block the potential shot/cross to prevent a goal and the tackling leg is not high, and has got the ball. His trailing leg has gone through Shaw, but it would take some incredible skill to go into a challenge thinking I'm going to win the ball cleanly with my lead tackling leg and snap him in half with my trailing leg, and pull it off.
You can make the argument that any tackle with enough force to break a leg is excessive and therefore should be a red, I can perfectly understand that. But the caf narrative that he's purposely gone to do Shaw some damage in this challenge I can't buy.