Why did Graf Spee not finish off Exeter?
Graf Spee initially concentrated her main armament on Exeter, starting fires and causing very severe damage. She then shifted target to the light cruisers who she then saw as her most dangerous opponents.
After scoring a damaging near-miss on Achilles, Graf Spee turned her fire back on Exeter in an attempt to finish her off but obtained no further hits and was soon forced to concentrate again on the light cruisers who were closing her fast and bringing the full force of their fire-power to bear, causing much superficial damage and many casualties.
Exeter, with all her guns out of action, was ordered to disengage and head for the Falkland Islands.