While Māui could not fly through Te Kā in his giant hawk form to get to Te Fiti before the incident where his magical fish hook was severely damaged
by the overpowered brofist with Te Kā, I can see he flies relatively close to the surface of the ocean.
Why doesn't Māui just fly higher and fly over Te Kā
(ggez), so Te Kā can't reach him by slamming him with its hand? Of course, the throwing fireball skill is an exception in this case. Instead of that he spent so much efforts to fight and get through Te Kā?