What is the meaning of "They fought so hard over who was to be king that the island broke in two" in the following sentences,
Up from the sea came not a fish, but a huge island. The island was the home of the mighty sea god. When the four older brothers saw the beautiful island, each one wanted to be its king, and they started to fight. They fought so hard over who was to be king that the island broke in two, and all the lazy brothers were drowned.
Does it mean "They who wanted to be king fought turning the wheel that the island broke in two ?
What does "so hard over" mean ?