This is unusual to pitch pole in such flat water...but it can happen if the boat is moving very slowly near DDW, main traveller out far, crew weight not right aft and then a big gust hits.

If the boat was going faster, the wind's impact would have been lessened and they would have made it.

PS: the image might look photoshopped if your browse doesn't show it full size...right click and view it in a separate window, resize to max...you can clearly see the carnoage on t he deck!