Mud is good bottom for anchoring. I'm sure the windlass brake and pall would fail long before the windlass was torn from the deck, not to mention the flukes on the anchor. I've seen the flukes get torn off a 15 ton anchor in Singapore. The windlass is still fine on that ship. Trying to drop anchor and put out the proper scope in blackness, in an emergency is a tall order for any crew. I bet they didn't have enough chain out.