[Big Papa Goat]

Because Old European Paganism is older then christianity. And the Jews didn't really interact that much with European pagans. And the only interaction that ever really happened between christians and pagans was prosetylization, unless I'm mistaken, and since it was the christians doing the prosetylizing, I don't think the pagans would have a lot of time to be adapting their symbols into their own religions, since they would be abandoning said religions at such a time as they became aware of christian symbols and so on.
That being said, it's reasonable to assume that early Christianity, being composed of a lot of people who were recently pagan would have retained a few of the symbols and so on that these people used to have.

Also, becoming a pagan seems to me like a pretty contrived and inauthentic idea.