It might be because the Jewish communities are very trusting. If someone needs money etc, they will rally together and raise it. Alternatively there are just weird people out there, especially hyper religious Christians with Jewish cosplay obsession.

Source: live in one

Pretending to be Jewish is a thing among some evangelical Christians. They assume a Jewish identity and then attempt to convert Jewish people to Christianity. However, I don't think this is what this man is doing. He's a grifter who used the Jewish faith to grift. Considering his social media presence, I wouldn't be surprised if he was angling for a reality show or something. There's lots of TV shows featuring big Christian families but none with big Jewish families which is what his social media is about.

Source: The Guardian (Evangelicals pretending to be Jewish.)

The Independent

He probably did it so faith based organizations would help facilitate adoptions, bettering his access to kids. They often try to keep kids in houses of the same religion in which they were previously raised and doing this gave him a leg up. I also suspect that he felt that he would be less likely examined if he were a religious man. This disgusting pervert knew what he was doing.

Maybe people are more likely to not ask questions if there's an intimidating cultural difference? Or maybe it's about claiming persecution? I have no idea.