If there were enough critters in my attic to feed a 6 ft. boa I think I’d want to clean the whole mess out, disinfect, paint, replace the insulation and seal the entry points.
Concur. A predator is never `100% efficient at removing rodents and vermin - a few will ALWAYS survive and breed and spread disease/odors/feces/parasites.
Remove the vermin, remove the predator(s), seal the area and access points, clean and fumigate, rinse, wash, repeat.
A 6 foot Boa can survive on a meal every month or so.
And weirdly enough, one of the Boa experts says that they grow faster with leaner diets.
So a half dozen vermin in the attic would have been more than enough to sustain him.