If 100% of iOS antivirus apps are fraud, that implies they do nothing (probably because of permissions) and/or there are no viruses on iOS to even find, no? If that's the case, that'd further imply those antivirus apps aren't, themselves, malware. Then... what's the point? Why would they exist as apps (and why would people download them) if they do nothing and gain nothing for the author or the user?
Because they think they need antivirus, they go searching on the App Store, and because Apple has totally failed in curation in this regard, they find them.
They subsequently don't get a virus, leave a five star review, and recommend it to their friends. See the Simpsons episode about the "anti-tiger rock".
If it's free it's probably making money from ads, or making money from your information. Or you paid for it and it's doing the above anyways. AV style apps can ask for a lot of permissions without raising as much as an eyebrow because they need them to 'protect' users, which puts them in a nice spot to data mine.