However, very few sailboats would be going 30 MPH at night.
Probably not. But I bet hitting that same hazard at 6 or 7 knots would screw at least the boat up pretty badly.
Much of the fault for this accident is due to excessive speed on the part of the boaters.
30 MPH is not excessive speed in open water.
[B]Furthermore, I am willing to bet that the old pier was marked on the charts to some degree or another...
One would think. One would also think the skipper had navigated that area before and should've known that hazard was there.