It is, but not impossible.
I was just a teen when it happened to me, but partly because I was lied to by the elders who studied with me.
You see I had relatives who tried hard to keep me away from it all. My parents were of no use, but I should have listened to what I learned from aunts, uncles, and cousins who kept telling me I was a "Mexican Jew," as they put it.
At 17 I didn't know what this meant, and I asked the elders who studied with me about it as they were preparing me for baptism. "My family tells me I can't get baptized because we are Mexican Jews."
The elders laughed. "There is no such thing," they assured me. "This is all that attack from Satan we warned you about that would happen."
A few years later I learned that it was no such Satanic attack. My family was trying to tell me I was from a group known as the "Mexican Jews of Monterrey." Monterrey, Mexico was settled and founded by some of the Jews who were expelled from Spain due to the Spanish Inquisition. The Inquisition followed them to Mexico, hunted them down, and chased them into Texas where my family settled.
Being uneducated is the worse thing you can be. The elders made a stupid assumption and told me there was no such thing as the "Mexican Jews" because they are religiously and historically ignorant. I was stupid enough to believe them because I was just a kid and didn't know my own ancestral history or its significance well enough.
Many Jews who convert to Christianity do it merely because of this lack of education in their own history. You are right that it is an enormous leap to make to become a JW. Catholicism is the only thing similar to Judaism in Christianity. Everything else is pretty much foreign and Gentile in nature. JWs are dripping in pagan practices and don't even know it. So for a Jew to make that leap is to be willing to assimilate into a culture that is foreign and anti-Semitic, something Jews can smell miles away unless they just don't know anything. There is nothing more evil in the eyes of Jews than assimilation...well, maybe genocide. So for an educated Jew to become a Witness would require embracing the principles that inspired Hitler.
I will tell you this. I learned of and verified my ancestral history while still a Witness. It did not take long after before I went rushing out. I didn't wait or fade either. I was giving a talk one day and gone the very next.
I look back at all those brochures and publications with illustrations of Paradise, and now I wonder how I could be so blind. Do you know what is missing from all those people dressed in different garb of different nationalities in the JWs pictures? Do you know what type of dress you never, ever see anyone wearing at one of those international conventions of Jehovah's Witnesses? You never see Jews.
You never see men wearing traditional head coverings known as kippah or yarmulke. You never see Jews in prayer shawls or women in Jewish dress. You never see Jewish men with full beards. You see none of this. The Watchtower is anti-Semitic. There are no Jews in their paradise, no Jewish culture left. No one from Israel is seen in traditional clothing at their conventions either. I'll bet your Jewish friend never got to wear his head covering in a Kingdom Hall or wear a beard or prayer shawl, am I right? They likely made him do what they made me do, assimilate from Jewish culture to pagan Western culture.
God's organization? Yeah, right!