Complex sentence: He is very instinctual-perhaps why he is such a good pilot-and frequently is able to come up with ingenious solutions to complicated problems-which some put down to his being a closet mathematical genius, despite little to no scientific training.
Split into simpler sentences: He is very instinctual-perhaps why he is such a good pilot-and frequently is able to come up with ingenious solutions to complicated problems. Some put this ability down to his being a closet mathematical genius, despite little to no scientific training.