There were many monasteries where beer and wine making were part of their business model.
The original vision for Benedict was a self-sufficient and isolated community, keeping interactions with the outside world to a minimum.
Wine is normally made from pure juice, and isn't heated at any point in the process. But again, it's made from pure juice: the inside of a grape is not a usual place to find dangerous bacteria, and on the outside one would normally find only the yeasts which produce the fermentation.
Modern wine-making washes the grapes thoroughly and adds yeast, the old-school method was simply to crush, and rely on the surface bloom and residual yeast in the vessel to do the work. Which lead to rather more vinegar than the modern vintner would tolerate.
Grape juice for wine, as it can’t be heated without ruining it, is usually lightly sulphited for a day or three before adding yeast, which kills the bacteria present in the juice.