This customer had fiberglass insulation installed (by others) to help cold floors above.
The before picture shows the unintended side effect of not treating a crawl space problem correctly. The contractor added fiberglass insulation in the crawlsapce ceiling and a plastic liner on the floor. They didn't address moisture in the crawl. The result was, that massive condensation and water in the space all summer. Moisture+ organic materials in a cool dark space = Mold.
The After picture shows all wet comtaminated materials removed. The space was treated with Mold X cleaner. The crawl was properly sealed and insulated. This #1 sloved the cold floor problem and #2 Keeps the crawl space dry year round, keeping the humidity below levels that mold needs to grow.