As this piece indicates, it was a varied and, moreover, convoluted set of confluences that brought Rome to its (ultimate) demise. And, even so, it was a very loooong path to the final precipice.
But the intrinsic matter that historians NEVER want to contemplate, when analysing what brought Rome to it's end (again, this was a very loooong path to the final precipice), is with how it was so ruptured on race and culture that it became totally dysfunctional. Because, Rome - well, at least its major cities and towns - were cabals of ethnocultural tribes which were all heaving and hoeing to assert their special and, moreover, self-serving interests.
Of course, this is the total mirror-image of exactly what's currently destroying the United States and, indeed, many Western nations, too, by virtue of large scale immigration intakes of people from diverse cultures and religions, too. Alas, the US, Britain, France and a other nations in western Europe, just as it was with Rome, are past their points of salvation because of diversity morphing into becoming divisive.