My guess is simply logistical redundancy. If the shipping lanes were impassible for some reason (blockade? ports damaged due to tsunami?), goods could still be

My guess is simply logistical redundancy. If the shipping lanes were impassible for some reason (blockade? ports damaged due to tsunami?), goods could still be sent/received via rail more cheaply than by air. Could also be a way to spur growth too. If you need to spend money on something, infrastructure seems like a decent choice.