The Japanese had some unusual tanks in WW2 in part because the tanks were developed and/or headed by naval department brains. This makes some sense really, as steel and armor are actually quite central to shipbuilding at the time, as are turrets.

So it isn't too surprising that tanks like the O-I, [seen next to a figurine for comparison of size,] look much like a small armored ship.

GuDeSt BoI