It used the widely used Mark 13 torpedo as a basis, with the addition of passive acoustic homing developed by Bell Labs.
It was recognized that US ships in the Pacific at this period were now heavily defended by AA, making attacks against them too costly to be successful.
Once the attacks against the Japanese home islands began, a similar challenge would be faced by the US Navy and so a weapon to defeat it would be needed.
Kingfisher began as a range extender for attacks against surface ships, although it was questioned whether these lighter torpedoes would be adequately effective against those targets.
As the British had discovered with Hedgehog and Squid, a flying weapon could arrive on the position of a detected target much faster than a torpedo could, so not allowing it time to evade or escape.