The Speed of mould.

Inspired by this thread, I’ve been thinking, Why does food go mouldy so quickly?

Back in my youth, I didn’t clean the house as often as I do these days. And food would grow a little furry coat fairly often. I was astounded by the speed it managed to get going. Even food in a sealed tub would suffer this fate, it would just take a bit longer.

Are mould spores really everywhere like it seems? Or was it just a symptom of the environment?