The opposing force divides in an attempt to catch the British line in a crossfire. That geometry only works when each separated group has enough ships to remain a serious and mutually supporting threat. Here the small detachments cannot prevent the concentrated British formation from surrounding one element at a time. Dividing the weaker force therefore invites defeat in detail despite the maneuver's tactical sophistication.
Notable Point · 3:49:29-3:50:38
Why a crossfire needs mutually supporting numbers
An enemy split intended to create a crossfire instead exposes isolated ships to a concentrated semicircle.