The former normally doesn’t care about God, one way or the other. Live and let live. Everyone else can believe what they want, type of thing. I respect that.
Atheists in the U.S at least, are people who typically hate God and hate those who believe in God, seeking to stamp out all traces of God in public and private in the U.S. Every atheist I’ve ever met was of this mold. As such, they do believe in God, because you can’t actively hate something you don’t believe exists. The hate is so great that even seeing a church or cross is often enough to cause a reaction. I’ve never enjoyed being around them because of that hateful nature. They are the people who attack others and then claim to be victims, those who seek to take what is the right of others’ under the law and then claim that their own rights are violated and so on. The only thing I’ve ever been able to figure out is that either 1. someone in a church hurt them personally and/or 2. they love to do something they know is wrong and it’s absolutely driving them bonkers.