Which factor of Roman decline had the most significant impact and why?

The phrase "the Fall of Rome" suggests that some cataclysmic event ended the Roman Empire, which stretched from the British Isles to Egypt and Iraq. But in the end, there was no straining at the gates, no barbarian horde that dispatched the Roman Empire in one fell swoop.  Instead, the Roman Empire fell slowly as a result of challenges from within and without, changing over the course of hundreds of years until its form was unrecognizable. Because of the long process, different historians have placed an end date at many different points on a continuum. Perhaps the Fall of Rome is best understood as a compilation of various maladies that altered a large swath of human habitation over many hundreds of years.

Explanation:

the answer is

a variant spelling of the word dote (british)