The Munson is fully loaded with iron ore pellets (indeed, for Indiana Harbor, IN) with relatively low freeboard compared to, say, a thousand foot ship like the Burns Harbor, which happens to be the only other ship to try to make an eastbound/downbound move away from western Lake Superior over the past day.
Lake Superior has been experiencing an unusually prolonged period of gale force winds over the past few days; those winds have been blowing strongly and their direction has kept shifting between northwest, west or southwest, and then northwest again. That weather situation is forecasted to persist through tomorrow (Nov 26, 2023) and into Monday (Nov 27, 2023).
Given the Munson's starting position and how the timing of the changes in weather would've coincided with the timing of the ship's theoretical progress across Lake Superior if they had tried to leave Duluth over the past day or two instead of staying at anchor, it seems likely that they could easily found themselves in a situation somewhere halfway across the lake where they were in big damaging waves with freezing spray causing ice buildup on the hull with limited options for turning aside and finding any shelter.
Sometimes the timing just isn't quite right, and patience is a virtue. By waiting at Duluth and getting underway only when they're sure they have a clear weather/timing "avenue" open ahead of them all the way across the big water to the shelter of the St Mary's River, they might actually end up making it to the Soo safer and/or sooner and/or with less fuel burned than if they'd tried to start heading down-bound "too soon" and had to slog it out in dangerous seas or make a major course deviation or risk a turn in a dangerous orientation with respect to big waves to try to make a run to shelter.