Oh, wait, you're not asking about the actual fall of the Roman Empire in 1453? You're asking about the non-event in 476 when the last Western Augustus retired to a villa near Naples, that Gibbon and the other "Enlightenment" historians trumped up as "the Fall of Rome" so they could dispossess the Christian Roman Empire with its capital moved to "New Rome" as Constantine the Great called it, Constantinople to everyone else, of its Romanity by inventing the fiction that it was a different "Byzantine" Empire, rather than the Roman Empire.
It's really hard for me to put much stock in trying to analyze deep social or political causes for the decision of the Eastern Augustus to stop having a Western counterpart and rule as sole Emperor.
Read a good history of the whole Roman Empire written by a competent "Byzantinist" who ignores Gibbons' propaganda, then circle back around and read Henri Pirenne's Mohammed and Charlemagne, to fill in the history of the West from 476 through to when the West stopped even theoretically being in the Roman Empire because it set up its own parallel version under Charlemagne (which as Voltaire waggishly noted was neither Holy, nor Roman, or -- after Charlemagne's death -- and Empire).
Gibbons writes extensively about Byzantium, state and church. I haven't finished my version, but it is going beyond the fall of the western empire. Chapter 71 covers 1430 AD. Of course, there are many abridged versions that may end abruptly, but mine doesn't. What is it, stylish now to trash Gibbons? His history is not perfect but still a benchmark by which others are measured.