How could the Navy destroyer collision happen?

Sailors watch pier-side as the Arleigh Burke-class guided-missile destroyer USS Fitzgerald (DDG 62) returns to Fleet Activities (FLEACT) Yokosuka following a collision with a merchant vessel while operating southwest of Yokosuka, Japan.
Sailors watch pier-side as the Arleigh Burke-class guided-missile destroyer USS Fitzgerald (DDG 62) returns to Fleet Activities (FLEACT) Yokosuka following a collision with a merchant vessel while operating southwest of Yokosuka, Japan.