Why do Atheists not believe in God?

I think there are primarily 4 reasons people do not believe in God.

1. They think the existence of a defined god or gods is contradictory, therefore impossible.

Some atheists think the existence of a God such as the Christian God is inconsistent with reality in a way that renders its existence impossible. Example: The Christian God is omnibonevolent. If that is the case, evil cannot exist. However, it is the case that evil does exist in many forms, some not a result of man. This means an omnibonevolent God cannot exist. Therefore the Christian God is impossible.

2. They think the existence of a defined god or gods is improbable given certain facts.

Some Atheists think the existence of a god such as the Christian God is improbable given certain facts about the world. Example: The Christian God is claimed to be the creator of both the universe and life. Current scientific evidence shows the universe may be self caused without need for a creator. Also, current scientific evidence shows that life may originate from non life due to natural processes that are not guided by intelligence. These two facts make some people believe the existence of a certain god such as the Christian God is improbable.

3. Emotional reasons.

Some Atheists do not believe in a god or gods because of emotional reasons, rather than intellectual ones. The existence of suffering, non answered prayers, and other personal grief leads some people to think that a god or gods does not exist, or is unlikely to exist due their emotional stress and their inability to cope with it.

4. Stupid reasons.

Some atheists think a god or gods does not exist for very stupid reasons. A simple example is people who claim the bible is a fairytale, therefore there is no god. This is a stupid reason to think a god or gods do not exist. A god or gods can exist independent of the truth of the bible. The bible can be completely false and man made while there is simultaneously a divine creator, or intelligent force in the universe. The thinking behind this is due to ignorance I would think.

Ill expand on this later if I must.