The ads they served were absolute bottom of the barrel awful, no legitimate brands, not even like clash of clans or anything - half their 'offers' were lockscreen ad APKs that installed themselves as unremovable device administrators that would kill play store and settings if you tried to open them.
If you played F2P games, mobile games, korean free MMOs probably starting from a few years ago, maybe half a decade ago, you will likely eventually remember SupersonicAds, Peanutlabs, Tapjoy (also purchased by ironsource), Matomy.
Tapjoy (now IS) would not pay out even after you installed the shitware: https://www.ftc.gov/news-events/news/press-releases/2021/01/...
SupersonicAds would collect IMEI, ESN, etc as long as they could https://www.ftc.gov/system/files/documents/public_events/122... + wrote code bad enough and delivered their loaders over plaintext http to the point that google play was blocking apps including their sdk at one point