I think this is probably one of those things where it appears something is the case b/c attention is focused there rather than somewhere else. LA has a big media industry and people looking for stories. So, there's a lot of resources already looking for something novel. On top of that people who are looking for attention purposely go there b/c of the potential of gaining that attention. None of that is going on in rural Utah. But anyone who's been out to rural Utah can tell you it's full of all sorts of weird off shoots of the LDS/Mormons.

And if your cult is doing something like having child brides/polygamy/something else of questionable legality, you probably don't want people to notice or be a member.

So, this may just be a perception and not have any basis of fact.

Also, b/c a cult isn't really an objective thing, mostly just a pejorative term used for groups that are found to be weird, it's incredibly hard to quantify.

But I would think, just based on what I've seen, is that there are more cults in places like Utah, where a religion is fairly new and has a culture of "prophets" that allow lots of splits, or places like West Virginia where specific communities are fairly isolated geographically and can develop in idiosyncratic ways b/c of that isolation.