When the apps ran, they opened a hidden browser window that loaded the ads and then interacted with them, making advertisers think they were reaching potential customers. In some cases it was not the developer’s intention but a third part modified them infecting with malware. Some of those apps were removed by Google but in many cases previously were millions downloads.
A such list is a little long and those are not all the misleading apps: Sparkle FlashLight, Snake Attack, Math Solver, Tak A Trip, Magnifeye, Join Up, Zombie Killer, Space Rocket, Neon Pong, Just Flashlight, Table Soccer, Cliff Diver, Box Stack, Jelly Slice, AK Blackjack, Color Tiles, Animal Match, Roulette Mania, HexaFall, HexaBlocks, PairZap. What people can do is to observe if after installing a new application the device runs a little hotter or if the battery life takes a hit. For the unexperieced users this can be a little difficult. So is better to be informed. Read the warnings when the experts issue them and be circumspect. Install only what you need.