What is the reason for the large area of moldy ceiling?

The ceiling is moldy for the following reasons:

The first reason: the ceiling is not firmly combined with outdoor cement, which will make rainwater enter the room through the gap, so there will be damp, moldy and hairy around the window.

Reason 2: When the living room was renovated, some interior walls of waterways were renovated, and the water pipes embedded in the ceiling leaked, resulting in the ceiling being damp and moldy.

Reason 3: Poor indoor air circulation leads to excessive indoor humidity, and wet ceilings and floating objects are easy to attach nutrients in indoor air and produce mold.