The correct answer to this open question is the following.
Unpredictable flooding of the rivers in Mesopotamia affected their government and religion in that Sumerians demanded the priests to maintain contact with Gods because they believed that the Gods were unpredictable and had different moods. They were the ones who sent catastrophes to the Earth such as the flooding of the rivers, earthquakes, or heavy rain. So rulers and people demanded priests to keep the gods happy through sacrifices. Sumerians believed that they were at the mercy of these strange and whimsical gods.
Let's remember that Sumera-Mesopotamia was settled in the middle of the Tigris and Euphrates Rivers. so the flooding of the rivers was a major problem for them.
