Mobile VPN affiliates are displaying scam ads that state your mobile device is infected, has been hacked, or is being tracked in order to scare visitors into purchasing a subscription. These ads attempt to scare or trick a user into installing a VPN app to resolve some sort of problem, whether that be to prevent a hacker from tracking them or to clean an infected device. The ads have been in circulation for quite some time, with reports going back as far back as last summer, so it is unknown if the promoted VPN apps are unaware of these ads.
Source: https://www.bleepingcomputer.com/news/security/mobile-vpns-promoted-by-you-are-infected-or-hacked-ads/