What caused the ship to sink? There are a couple of theories cited in the "Marine Casualty Report" by the US. Coast Guard Marine Board of Investigation Report. Since there were no survivors nor witnesses, their report is based on testimonies and an underwater survey of the wreck. This report suggests that the Fitzgerald was taking on water due to earlier damage from the storm and that around 7:15 p.m. it plunged headfirst into a large wave and sank abruptly.
That's right! It's coming back to me now. There have been many theories, It seems your post is correct. I now recall the that the ship took on water and torpedoed to the bottom when it met a wave at a most unfortunate angle.