God has always existed.
That's just your belief, and the only reason you believe it is because you happen to have been born in a place and time where Christianity is popular. The Judeo-Christian God was invented BY PEOPLE only a mere few thousand years ago, a blink of an eye considering the earth has existed for billions of years. If you'd been born a few thousand years ago, you'd insist that Mithras has always existed, or Zeus has always existed, or Ra has always existed.
For thousands of years, people believed that a great deity named Atum created the universe. Now not a single person alive still worships Atum, and hardly anyone except scholars have ever even heard of him. Does the fact that no one still believes in or knows about Atum mean that he did not, in fact, create the universe? Similiarly, if the true creator of the universe was God and not Atum, when people forget all about God and there's not a single Christian alive, does that mean that God didn't create the universe? None of us know for sure how the universe was created.
I mean IF a creator deity ever existed, he/she/it certainly existed billions of years before humans gave him/her/it a name.
Considering that people believed the earth was created by Atum for a hell of a lot longer than people believed earth was created by God, does that not suggest it's more likely that Atum was the true creator? No, because nothing humans invent billions of years afterwards has the power to change anything about the dawn of the universe.
Judaism has existed from the very first book of the Bible.
Judaism has existed about 4000 years. But the Bible was not written till many hundreds of years after Judaism was established. Humans have existed for 300,000 years.