I figure the one just sat around for longer, as I've had extra blue-y cheese develop in my own fridge. Just never seen such a striking difference at the store, which I found mildly interesting.
I use molds to ferment vegetables (think sauerkraut, but with squash, or cauliflower, or fennel, or leek...), to make soda (kombucha, often with apples or blackberry), to bake bread.
Coffee beans are fermented, too. And many other foodstuff.
Bacterias are our best friends. So tasty.