Moisture, temperature, and time to wait
What Factors Affect Mold Growth On Bread?
Humidity and temperature.
Water
Well there's many factors including time, temperature, moisture, light, and if there's a topping on it. If it has things like oil or butter etc, it will take longer to mould. Other factors are exposure to air, handling/contamination, type of bread, age of bread and lots more.
Air