Here are two kinds of statement:
"Potato blight" has no single cause -- it results from combinations of inter-related agricultural conditions, including rainy summers, witchcraft, overworked soils, and God's wrath at our tolerance for rampant homosexuality.
"Potato blight" is the common name for a plant disease, usually caused by the organism Phytophthora infestans.
The first statement, just in its form, is essentially pre-scientific, pre-rational thinking, which has been the norm for most of human history. Parts of it may be true in some sense. Pretty much none of it is in any way testable.
The second is a scientific statement at least in form -- it may or may not be accurate, but that's easy to check.
Occam's basic point was that when you propose a complex, multi-causal explanation of a discrete syndrome, against an alternative hypothesis which is parsimonious, precise and uni-causal, the Bayesian prior of the complex hypothesis should be very low.
In this case, we have a multi-causal explanation of a historical mass migration. To my mind, the causal null hypothesis for any urban decline or mass migration, past or present, is: the city fell into ruins because the people who lived there left. The people left because, due to political or military forces, they became afraid for their physical safety. In short, ethnic cleansing.
This simple uni-causal explanation is amply confirmed by anecdotal evidence from the period. Or you could accept Wikipedia's multi-causal explanation, which to my eye is basically zoning changes, the phase of the moon and maybe even God's wrath.
But, sure, there are a ton of papers. Bear in mind: in 1405, there were a ton of papers as well.