Pop quiz: Winston Churchill uses passive voice

The gratitude of every home in our island, in our Empire, and indeed throughout the world except in the abodes of the guilty goes out to the British airmen who, undaunted by odds, unweakened by their constant challenge and mortal danger, are turning the tide of world war by their prowess and their devotion.

Never in the field of human conflict was so much owed by so many to so few. (Prolonged cheers.)

Winston Churchill 1940

Active voice: People owed gratitude. (many owed so much…)
Passive voice: Gratitude was owed by people. (so much was owed…)

Revised sentence, using active voice:

Never in the field of human conflict did so many owe so much to so few.

Question: Why did Churchill choose the passive voice in this sentence?

ANSWER