Why historical organs are tuned in different pitch levels?

In one of my previous videos, I have already discussed Chorton and Kammerton, pitch levels which differ from our modern A - 440 Hz approximately by the half step up or down. Hopefully these terms make sense to you now. But in the above video I didn't explain the reason why the tuning of these organs was based on different pitch levels. In case you are still wandering, here is my answer.