Jews can be as diverse as anyone else, but I never understood why my friend would live kosher and eat kosher if he was an atheist. Yet he did. He said it was a cultural thing. What good is any religion if it doesn't address the afterlife or the judgment of man?
Judaism is not a religion of belief or faith. It is one of action, where people cooperate with God to bring practical healing and help into the world.
Technically speaking, Jews don't "believe" in God. None of us have this "belief." But that doesn't mean that Jews don't accept God as real.
In Gentile religions it seems to be important to many of them that one have "faith" in a set of creeds or theological concepts. Jews don't (and many actually won't) do this. This type of "faith" is a mental assent that a certain concept or doctrine is true, something one has to guard from doubt. In the Jewish mind, real things don't require belief or faith.
One does not "believe" in their existence on the planet earth or "guard their faith" in the existence of their family from doubt. Why not? These things are real. Our existence on earth and the existence of our family members is not affected by how much or how little belief we have in their existence. They exist, and no amount of belief or faith is necessary.
God is no different for Jews. God is real. We are Jews only because we are in a covenant with God. Without God there would be no covenant, and without the covenant there would be no people known as the Jews. If I, a Jew, exist and my people exist, then no belief is necessary in any of this. All these elements are therefore real.
But since God is not a deity in the sense "deity" is usually understood in non-Jewish religion, some Jews are atheist. On the flip side, not all Jews who will say "I don't believe in God" are atheist either. And not all Jews who will say they do believe in God will be Torah observant.
This can be confusing to Gentiles because in their culture religion is about what one believes. In Jewish culture, religion is what one does. A person can claim they believe in a concept but have doubts or weak faith. A challenge may cause them to act contrary to their claimed convictions. Yet in Judaism, one's convictions can only be judged by one's actions. We don't "walk the talk." Instead Jew merely walk. The "talk" has no value as Judaism is about bringing practical, useful benefits into the world. A person's mere mental assent that some religious concept is real cannot guarantee this.
We are not focused on an afterlife as we have the miracles of a present life. Every breath we have now is a gift. Every moment of life is a miracle. Every second is this life is a second experiencing God who Jews accept as real as the world they live in. We have no need for belief or faith as we are already with God now. Any future life is guaranteed by the covenant we keep. (And yes, the covenant relationship has not ended, just changed over the years.)
Since Jews do not accept the Christian belief of the Fall of Man, there is no judgment of man necessary. God judged man at creation when God pronounced us "good." The narrative of Eden merely introduces the "wrestling" with God by which Jacob and we inherited the name "Israel."
Jews do not see wrestling with God as a Fall, but as the sign that we are in a covenant. Partners in a covenant often wrestle with another. This "wrestling" occurs because both are working to bring healing into the world through Torah, a process we call "Tikkun Olam." We don't always see eye-to-eye on how best to do this like most partners in a legally binding contract, but when either side refuses to do it the way the other wants it isn't always a literal sin. Eventually one side gives in to the other, sometimes there is compromise. But a Fall of Man has never occurred. God wants partners in Tikkun Olam, not blind slaves.
Our religion is our culture. You cannot ask us to leave one behind without leaving the other behind as they are one. Thus a Jew may not believe in God and keep kosher (technically speaking, I don't "believe" in God because things that are real don't require my faith, as they exist whether I acknowledge them or not). Our religion is not a belief system. Judaism is how we express who we are.