"Mold is a sign of a moisture problem", for mold to survive it must have the right environment and a food source that is wet enough long enough. To properly correct a mold problem you have to first fix the moisture problem, if you only treat the symptom (the mold) the problem will return.
The cabinet blocked air flow that would have helped remove dampness, this caused the drywall to be "Wet enough Long enough" in an isolated area creating the right environment for mold growth.
Vacant house that did not have the heating or cooling system on for a long period of time. This caused excessive moisture in the air that saturated the paper on the drywall and caused mold growth.
Heated air from the ducts hitting the poorly insulated wall caused condensation behind the paneling and promoted mold grow. This was not found until remodeling was started.
Hot moist air from a bathroom vent fan was discharged directly on the roof sheathing , this isolated the moisture and kept it constantly wet.
Hot humid outside air hits the cold duct work in the crawl space and causes condensation in the summer. This can cause a musty smell in your home from the soil being constantly wet.