"From what I've read", though, one of the variables was that EF's main hatches weren't battened down all the way, which made the ship vulnerable to water getting into the hold. Seems that the company didn't want to pay the overtime for that...
Lots of other aspects too... one of them being that Captain McSorley was under pressure to make the delivery on time...
One would hope that those, and other issues have been addressed, after the fact...
There are also two other explanations. One is that there was a wave under the bow and another on the stern. The fully loaded ship and the bottom just dropped out.
The other explanation came after sounding were taken of the bottom of the lake. It appears there was some shallow water and the EF simply ran aground and torn it bottom out.
Also, Lake iron ore carriers do not have water tight compartments.