The rogue waves is probably the most likely cause of the event. The ship was fully loaded with iron ore pellets and a wave at the bow and a wave at the stern lifted the ship up and she broke in two. Also, I believe the Fitzgerald had been lengthen and that might have caused a weakness in the hull.
However, there are two other theories about the sinking:
first, after the sinking new soundings were taken of the bottom. The water was not as deep as previous thought and it is possible that with the storm the Fitzgerald scraped the bottom of the lake and torn its bottom out. Second, the hatches were not properly secured and water leaked in or the vents to the cargo holes took on water.
I have spoken to several now retired Coast Guard officers who were involved in the investigation. They don’t know for sure what the cause was.
Also, a few years ago, Gordon Lightfoot changed some lyrics when they found the main hatchway did not give in.
I met a guy once who dove the wreck. He thinks some of the hatch bolts weren’t tightened all the way and water came in to the hold, making the ship heavier and harder to control.