How does the conclusion of "The Pit in the Pendulum" impact its overall meaning?

The final paragraph of Edgar Allan Poe's 1842 story is

"There was a discordant hum of human voices! There was a loud blast as of many trumpets! There was a harsh grating as of a thousand thunders! The fiery walls rushed back! An outstretched arm caught my own as I fell, fainting, into the abyss. It was that of General Lasalle. The French army had entered Toledo. The Inquisition was in the hands of its enemies."

What is revealed in these final eight sentences is the reason the narrator has been imprisoned and tortured. He has been held in Toledo, Spain, during the period known as the Spanish Inquisition, when the monarchs Ferdinand and Isabella sought to make Spain exclusively Catholic and purge it of nonbelievers.
The overall meaning of the story is found in how the narrator experiences his captivity. The focus is on the sounds and sensations he hears and feels and the terror he experiences. His miraculous escape from the blade because of his own cleverness and the arrival of his high-ranking savior makes for a dramatic story.
Poe apparently was not concerned with historical facts, though, because General Lasalle did not lead the French troops that invaded Toledo during Napoleon's campaign in the Peninsular War (1807–1814).