'Ilov80s said:
Regardless, Tywin obviously didn't trust Tyrion to defend the city (rightly so), it won't be very difficult to write Tyrion out of the victory...what did Tyrion really do anyway? He launched the wildfire which Cersei had made.
Cersei's plan was to launch jars of wildfire at Stannis's troops with catapults. As Bronn pointed out, some wildfire would have been thrown back over the wall in that case, and the city, or substantial parts of it, may have burned.Tyrion's much better idea was to send one boat out into the harbor leaking wildfire, and then light it all up from long distance with a flaming arrow.
He planned some sneak attack which ended up with his men getting attacked from behind.
He rallied and led the troops when Joffrey and the Hound would not, and the rest of the Lannister army inside the wall was ready to call it quits. Even if that didn't have a big effect on the outcome, it showed leadership that nobody else in the city could match.