mushroom in the bathroom

8am

8pm

Last week had some fungi mushroom growing in the bathroom. The night before I noticed some white round thing like mini marshmallows sticking out from the back of the cabinet (should have taken photos of that). Then the next morning they had grown into mushrooms!! After work when I got home they were dead! Not sure why and what triggered the growth as the back of the cabinet is clean, might be the moist in the bathroom. Anyway, they sure have very short lifespan.