I mean - it definitely depends. Besides my uncle I've known a handful of Black Israelites who have varying degrees of belief but in my experience, it is usually a fringe belief in the sense that you have to be exposed to some facet of by someone/something. You're far less likely to just learn about it in school or at a bar. My uncle definitely discovered it through Facebook. It doesn't help that the local Christian church they go to is very pro-Israel either though. I'd imagine if you lived somewhere like NYC where you can find a group of Black Israelite preachers in public on the sidewalk, it may be a little easier to get into.