According to Google, the banned apps were engaging in ad fraud activities, a practice that has the "potential to harm users, advertisers and publishers." They violated the policies related to disruptive ads which they all agreed to and disallowed interstitial.
"We define disruptive ads as ads that are displayed to users in unexpected ways, including impairing or interfering with the usability of device functions," Google said.
Not only were they banned from Play Store, they were also banned from Google Admob and Google Ad manager which are all Google's ad monetization platforms.
Google's disruptive ad policy specifically targets ads that are displayed to users in unexpected ways, especially out-of-context ads that can disrupt device functionality. Such kind of ads may include, for example, full-screen ads served when when users attempt to make phone calls, unlock their phones or even when the phone isn't being used.
Intrusive ads on apps on the Android platform has been an issue that Google has been combating for years now.
The Internet giant has stated its continued commitment towards developing new technologies using machine learning to protect against disruptive ads deployed by malicious developers.
"As we move forward, we will continue to invest in new technologies to detect and prevent emerging threats that can generate invalid traffic, including disruptive ads, and to find more ways to adapt and evolve our platform and ecosystem policies to ensure that users and advertisers are protected from bad behaviour," Google said.